0.019801 0.000000 0.000000 0.000000 0.017263 0.000000 0.000000 0.000000 0.016228 0.00000 0.00000 0.00000 Foulkes, J.E. Prabu-Jeyabalan, M. Cooper, D. Schiffer, C.A. http://mmcif.pdb.org/dictionaries/ascii/mmcif_pdbx.dic 8 90.00 90.00 90.00 50.50 57.93 61.62 C3 H7 N O2 89.093 y ALANINE L-peptide linking C6 H15 N4 O2 1 175.209 y ARGININE L-peptide linking C4 H8 N2 O3 132.118 y ASPARAGINE L-peptide linking C4 H7 N O4 133.103 y ASPARTIC ACID L-peptide linking C3 H7 N O2 S 121.158 y CYSTEINE L-peptide linking C11 H19 N O2 197.274 2-METHYL-DECAHYDRO-ISOQUINOLINE-3-CARBOXYLIC ACID non-polymer C5 H10 N2 O3 146.144 y GLUTAMINE L-peptide linking C5 H9 N O4 147.129 y GLUTAMIC ACID L-peptide linking C2 H5 N O2 75.067 y GLYCINE peptide linking C6 H10 N3 O2 1 156.162 y HISTIDINE L-peptide linking H2 O 18.015 WATER non-polymer C9 H13 N O2 167.205 n (2S)-2-amino-3-phenylpropane-1,1-diol (2S)-2-amino-3-phenylpropane-1,1-diol peptide-like C6 H13 N O2 131.173 y ISOLEUCINE L-peptide linking C6 H13 N O2 131.173 y LEUCINE L-peptide linking C6 H15 N2 O2 1 147.195 y LYSINE L-peptide linking C5 H11 N O2 S 149.211 y METHIONINE L-peptide linking C4 H11 N 73.137 TERTIARY-BUTYLAMINE non-polymer C9 H11 N O2 165.189 y PHENYLALANINE L-peptide linking O4 P -3 94.971 PHOSPHATE ION non-polymer C5 H9 N O2 115.130 y PROLINE L-peptide linking C10 H7 N O2 173.168 quinoline-2-carboxylic acid non-polymer C3 H7 N O3 105.093 y SERINE L-peptide linking C4 H9 N O3 119.119 y THREONINE L-peptide linking C11 H12 N2 O2 204.225 y TRYPTOPHAN L-peptide linking C9 H11 N O3 181.189 y TYROSINE L-peptide linking C5 H11 N O2 117.146 y VALINE L-peptide linking N 1 N N N 2 S C N 3 N C N 4 N O N 5 N C N 6 N O N 7 N H N 8 N H N 9 N H N 10 N H N 11 N H N 12 N H N 13 N H N 14 N N N 15 S C N 16 N C N 17 N O N 18 N C N 19 N C N 20 N C N 21 N N N 22 N C N 23 N N N 24 N N N 25 N O N 26 N H N 27 N H N 28 N H N 29 N H N 30 N H N 31 N H N 32 N H N 33 N H N 34 N H N 35 N H N 36 N H N 37 N H N 38 N H N 39 N H N 40 N H N 41 N N N 42 S C N 43 N C N 44 N O N 45 N C N 46 N C N 47 N O N 48 N N N 49 N O N 50 N H N 51 N H N 52 N H N 53 N H N 54 N H N 55 N H N 56 N H N 57 N H N 58 N N N 59 S C N 60 N C N 61 N O N 62 N C N 63 N C N 64 N O N 65 N O N 66 N O N 67 N H N 68 N H N 69 N H N 70 N H N 71 N H N 72 N H N 73 N H N 74 N N N 75 R C N 76 N C N 77 N O N 78 N C N 79 N S N 80 N O N 81 N H N 82 N H N 83 N H N 84 N H N 85 N H N 86 N H N 87 N H N 88 N N N 89 N C N 90 S C N 91 N C N 92 N O N 93 N C N 94 S C N 95 N C N 96 N C N 97 N C N 98 N C N 99 S C N 100 N C N 101 N O N 102 N H N 103 N H N 104 N H N 105 N H N 106 N H N 107 N H N 108 N H N 109 N H N 110 N H N 111 N H N 112 N H N 113 N H N 114 N H N 115 N H N 116 N H N 117 N H N 118 N H N 119 N H N 120 N H N 121 N N N 122 S C N 123 N C N 124 N O N 125 N C N 126 N C N 127 N C N 128 N O N 129 N N N 130 N O N 131 N H N 132 N H N 133 N H N 134 N H N 135 N H N 136 N H N 137 N H N 138 N H N 139 N H N 140 N H N 141 N N N 142 S C N 143 N C N 144 N O N 145 N C N 146 N C N 147 N C N 148 N O N 149 N O N 150 N O N 151 N H N 152 N H N 153 N H N 154 N H N 155 N H N 156 N H N 157 N H N 158 N H N 159 N H N 160 N N N 161 N C N 162 N C N 163 N O N 164 N O N 165 N H N 166 N H N 167 N H N 168 N H N 169 N H N 170 N N N 171 S C N 172 N C N 173 N O N 174 N C Y 175 N C Y 176 N N Y 177 N C Y 178 N C Y 179 N N N 180 N O N 181 N H N 182 N H N 183 N H N 184 N H N 185 N H N 186 N H N 187 N H N 188 N H N 189 N H N 190 N H N 191 N O N 192 N H N 193 N H N 194 N C N 195 N O N 196 S C N 197 N N N 198 N C Y 199 N C Y 200 N C Y 201 N C Y 202 N C Y 203 N C Y 204 N C N 205 N O N 206 N H N 207 N H N 208 N H N 209 N H N 210 N H N 211 N H N 212 N H N 213 N H N 214 N H N 215 N H N 216 N H N 217 N H N 218 N H N 219 N N N 220 S C N 221 N C N 222 N O N 223 S C N 224 N C N 225 N C N 226 N C N 227 N O N 228 N H N 229 N H N 230 N H N 231 N H N 232 N H N 233 N H N 234 N H N 235 N H N 236 N H N 237 N H N 238 N H N 239 N H N 240 N H N 241 N N N 242 S C N 243 N C N 244 N O N 245 N C N 246 N C N 247 N C N 248 N C N 249 N O N 250 N H N 251 N H N 252 N H N 253 N H N 254 N H N 255 N H N 256 N H N 257 N H N 258 N H N 259 N H N 260 N H N 261 N H N 262 N H N 263 N N N 264 S C N 265 N C N 266 N O N 267 N C N 268 N C N 269 N C N 270 N C N 271 N N N 272 N O N 273 N H N 274 N H N 275 N H N 276 N H N 277 N H N 278 N H N 279 N H N 280 N H N 281 N H N 282 N H N 283 N H N 284 N H N 285 N H N 286 N H N 287 N H N 288 N N N 289 S C N 290 N C N 291 N O N 292 N C N 293 N C N 294 N S N 295 N C N 296 N O N 297 N H N 298 N H N 299 N H N 300 N H N 301 N H N 302 N H N 303 N H N 304 N H N 305 N H N 306 N H N 307 N H N 308 N N N 309 N C N 310 N C N 311 N C N 312 N C N 313 N H N 314 N H N 315 N H N 316 N H N 317 N H N 318 N H N 319 N H N 320 N H N 321 N H N 322 N H N 323 N H N 324 N N N 325 S C N 326 N C N 327 N O N 328 N C Y 329 N C Y 330 N C Y 331 N C Y 332 N C Y 333 N C Y 334 N C N 335 N O N 336 N H N 337 N H N 338 N H N 339 N H N 340 N H N 341 N H N 342 N H N 343 N H N 344 N H N 345 N H N 346 N H N 347 N P N 348 N O N 349 N O N 350 N O N 351 N O N 352 N N N 353 S C N 354 N C N 355 N O N 356 N C N 357 N C N 358 N C N 359 N O N 360 N H N 361 N H N 362 N H N 363 N H N 364 N H N 365 N H N 366 N H N 367 N H N 368 N H N 369 N C N 370 N O Y 371 N N Y 372 N C Y 373 N C Y 374 N C Y 375 N C Y 376 N C Y 377 N C Y 378 N C Y 379 N C Y 380 N C N 381 N O N 382 N H N 383 N H N 384 N H N 385 N H N 386 N H N 387 N H N 388 N H N 389 N N N 390 S C N 391 N C N 392 N O N 393 N C N 394 N O N 395 N O N 396 N H N 397 N H N 398 N H N 399 N H N 400 N H N 401 N H N 402 N H N 403 N N N 404 S C N 405 N C N 406 N O N 407 R C N 408 N O N 409 N C N 410 N O N 411 N H N 412 N H N 413 N H N 414 N H N 415 N H N 416 N H N 417 N H N 418 N H N 419 N H N 420 N N N 421 S C N 422 N C N 423 N O N 424 N C Y 425 N C Y 426 N C Y 427 N C Y 428 N N Y 429 N C Y 430 N C Y 431 N C Y 432 N C Y 433 N C N 434 N O N 435 N H N 436 N H N 437 N H N 438 N H N 439 N H N 440 N H N 441 N H N 442 N H N 443 N H N 444 N H N 445 N H N 446 N H N 447 N N N 448 S C N 449 N C N 450 N O N 451 N C Y 452 N C Y 453 N C Y 454 N C Y 455 N C Y 456 N C Y 457 N C N 458 N O N 459 N O N 460 N H N 461 N H N 462 N H N 463 N H N 464 N H N 465 N H N 466 N H N 467 N H N 468 N H N 469 N H N 470 N H N 471 N N N 472 S C N 473 N C N 474 N O N 475 N C N 476 N C N 477 N C N 478 N O N 479 N H N 480 N H N 481 N H N 482 N H N 483 N H N 484 N H N 485 N H N 486 N H N 487 N H N 488 N H N 489 N H N 1 N sing N 2 N sing N 3 N sing N 4 N sing N 5 N sing N 6 N sing N 7 N doub N 8 N sing N 9 N sing N 10 N sing N 11 N sing N 12 N sing N 13 N sing N 14 N sing N 15 N sing N 16 N sing N 17 N sing N 18 N sing N 19 N doub N 20 N sing N 21 N sing N 22 N sing N 23 N sing N 24 N sing N 25 N sing N 26 N sing N 27 N sing N 28 N sing N 29 N sing N 30 N sing N 31 N sing N 32 N sing N 33 N doub N 34 N sing N 35 N sing N 36 N sing N 37 N sing N 38 N sing N 39 N sing N 40 N sing N 41 N sing N 42 N sing N 43 N sing N 44 N sing N 45 N doub N 46 N sing N 47 N sing N 48 N sing N 49 N sing N 50 N doub N 51 N sing N 52 N sing N 53 N sing N 54 N sing N 55 N sing N 56 N sing N 57 N sing N 58 N sing N 59 N sing N 60 N sing N 61 N doub N 62 N sing N 63 N sing N 64 N sing N 65 N sing N 66 N doub N 67 N sing N 68 N sing N 69 N sing N 70 N sing N 71 N sing N 72 N sing N 73 N sing N 74 N sing N 75 N sing N 76 N doub N 77 N sing N 78 N sing N 79 N sing N 80 N sing N 81 N sing N 82 N sing N 83 N sing N 84 N sing N 85 N sing N 86 N sing N 87 N sing N 88 N sing N 89 N sing N 90 N sing N 91 N sing N 92 N doub N 93 N sing N 94 N sing N 95 N sing N 96 N sing N 97 N sing N 98 N sing N 99 N sing N 100 N sing N 101 N sing N 102 N sing N 103 N sing N 104 N sing N 105 N sing N 106 N sing N 107 N sing N 108 N sing N 109 N sing N 110 N sing N 111 N sing N 112 N sing N 113 N sing N 114 N sing N 115 N sing N 116 N sing N 117 N sing N 118 N sing N 119 N sing N 120 N sing N 121 N sing N 122 N sing N 123 N doub N 124 N sing N 125 N sing N 126 N sing N 127 N sing N 128 N sing N 129 N sing N 130 N sing N 131 N doub N 132 N sing N 133 N sing N 134 N sing N 135 N sing N 136 N sing N 137 N sing N 138 N sing N 139 N sing N 140 N sing N 141 N sing N 142 N doub N 143 N sing N 144 N sing N 145 N sing N 146 N sing N 147 N sing N 148 N sing N 149 N sing N 150 N doub N 151 N sing N 152 N sing N 153 N sing N 154 N sing N 155 N sing N 156 N sing N 157 N sing N 158 N sing N 159 N sing N 160 N doub N 161 N sing N 162 N sing N 163 N sing N 164 N sing N 165 N sing N 166 N sing N 167 N sing N 168 N sing N 169 N doub N 170 N sing N 171 N sing N 172 N sing N 173 N sing Y 174 N sing Y 175 N doub Y 176 N doub N 177 N sing Y 178 N sing N 179 N sing Y 180 N sing N 181 N sing N 182 N sing N 183 N sing N 184 N sing N 185 N sing N 186 N sing N 187 N sing N 188 N sing N 189 N sing N 190 N sing N 191 N sing N 192 N sing N 193 N sing N 194 N sing N 195 N sing N 196 N sing N 197 N sing Y 198 N doub Y 199 N sing Y 200 N sing N 201 N sing Y 202 N doub N 203 N sing Y 204 N doub N 205 N sing Y 206 N sing N 207 N sing N 208 N sing N 209 N sing N 210 N sing N 211 N sing N 212 N sing N 213 N sing N 214 N sing N 215 N sing N 216 N sing N 217 N doub N 218 N sing N 219 N sing N 220 N sing N 221 N sing N 222 N sing N 223 N sing N 224 N sing N 225 N sing N 226 N sing N 227 N sing N 228 N sing N 229 N sing N 230 N sing N 231 N sing N 232 N sing N 233 N sing N 234 N sing N 235 N sing N 236 N sing N 237 N sing N 238 N doub N 239 N sing N 240 N sing N 241 N sing N 242 N sing N 243 N sing N 244 N sing N 245 N sing N 246 N sing N 247 N sing N 248 N sing N 249 N sing N 250 N sing N 251 N sing N 252 N sing N 253 N sing N 254 N sing N 255 N sing N 256 N sing N 257 N sing N 258 N sing N 259 N doub N 260 N sing N 261 N sing N 262 N sing N 263 N sing N 264 N sing N 265 N sing N 266 N sing N 267 N sing N 268 N sing N 269 N sing N 270 N sing N 271 N sing N 272 N sing N 273 N sing N 274 N sing N 275 N sing N 276 N sing N 277 N sing N 278 N sing N 279 N sing N 280 N sing N 281 N sing N 282 N sing N 283 N doub N 284 N sing N 285 N sing N 286 N sing N 287 N sing N 288 N sing N 289 N sing N 290 N sing N 291 N sing N 292 N sing N 293 N sing N 294 N sing N 295 N sing N 296 N sing N 297 N sing N 298 N sing N 299 N sing N 300 N sing N 301 N sing N 302 N sing N 303 N sing N 304 N sing N 305 N sing N 306 N sing N 307 N sing N 308 N sing N 309 N sing N 310 N sing N 311 N sing N 312 N sing N 313 N sing N 314 N sing N 315 N sing N 316 N sing N 317 N doub N 318 N sing N 319 N sing N 320 N sing N 321 N sing Y 322 N doub Y 323 N sing Y 324 N sing N 325 N sing Y 326 N doub N 327 N sing Y 328 N doub N 329 N sing Y 330 N sing N 331 N sing N 332 N sing N 333 N sing N 334 N doub N 335 N sing N 336 N sing N 337 N sing N 338 N sing N 339 N sing N 340 N sing N 341 N sing N 342 N sing N 343 N sing N 344 N doub N 345 N sing N 346 N sing N 347 N sing N 348 N sing N 349 N sing N 350 N sing N 351 N sing N 352 N sing N 353 N sing N 354 N sing N 355 N sing N 356 N doub N 357 N sing Y 358 N doub Y 359 N sing Y 360 N doub Y 361 N sing N 362 N sing N 363 N sing N 364 N sing Y 365 N doub N 366 N sing Y 367 N sing N 368 N sing Y 369 N doub Y 370 N sing N 371 N sing Y 372 N doub Y 373 N sing Y 374 N sing N 375 N sing N 376 N sing N 377 N sing N 378 N sing N 379 N sing N 380 N sing N 381 N sing N 382 N doub N 383 N sing N 384 N sing N 385 N sing N 386 N sing N 387 N sing N 388 N sing N 389 N sing N 390 N sing N 391 N sing N 392 N sing N 393 N sing N 394 N sing N 395 N doub N 396 N sing N 397 N sing N 398 N sing N 399 N sing N 400 N sing N 401 N sing N 402 N sing N 403 N sing N 404 N sing N 405 N sing N 406 N sing N 407 N sing N 408 N sing N 409 N sing N 410 N sing N 411 N doub N 412 N sing N 413 N sing N 414 N sing N 415 N sing Y 416 N doub Y 417 N sing Y 418 N sing N 419 N sing Y 420 N doub Y 421 N sing Y 422 N sing N 423 N sing Y 424 N sing Y 425 N doub N 426 N sing Y 427 N doub N 428 N sing Y 429 N sing N 430 N sing N 431 N sing N 432 N sing N 433 N sing N 434 N sing N 435 N sing N 436 N sing N 437 N sing N 438 N sing N 439 N doub N 440 N sing N 441 N sing N 442 N sing N 443 N sing Y 444 N doub Y 445 N sing Y 446 N sing N 447 N sing Y 448 N doub N 449 N sing Y 450 N doub N 451 N sing Y 452 N sing N 453 N sing N 454 N sing N 455 N sing N 456 N sing N 457 N sing N 458 N sing N 459 N sing N 460 N sing N 461 N sing N 462 N sing N 463 N doub N 464 N sing N 465 N sing N 466 N sing N 467 N sing N 468 N sing N 469 N sing N 470 N sing N 471 N sing N 472 N sing N 473 N sing N 474 N sing US J.Virol. JOVIAM 0825 0022-538X 80 6906 6916 10.1128/JVI.01900-05 16809296 Role of invariant Thr80 in human immunodeficiency virus type 1 protease structure, function, and viral infectivity. 2006 10.2210/pdb2fgu/pdb pdb_00002fgu 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 0.00000 0.00000 0.00000 100 1 Osmic Mirrors IMAGE PLATE 2004-11-05 RIGAKU RAXIS IV Osmic Mirrors SINGLE WAVELENGTH M x-ray 1 1.5418 1.0 1.5418 ROTATING ANODE RIGAKU 10787.736 Protease 3.4.23.16 Q7K, I64V, T80S 2 man polymer 94.971 PHOSPHATE ION 5 syn non-polymer 173.168 quinoline-2-carboxylic acid 1 syn non-polymer 132.118 ASPARAGINE 1 syn non-polymer 167.205 (2S)-2-amino-3-phenylpropane-1,1-diol 1 syn non-polymer 197.274 2-METHYL-DECAHYDRO-ISOQUINOLINE-3-CARBOXYLIC ACID 1 syn non-polymer 73.137 TERTIARY-BUTYLAMINE 1 syn non-polymer 18.015 water 130 nat water Retropepsin, PR no no PQITLWKRPLVTIRIGGQLKEALLDTGADDTVLEEMNLPGKWKPKMIGGIGGFIKVRQYDQIPVEICGHKAIGTVLVGPS PVNIIGRNLLTQIGCTLNF PQITLWKRPLVTIRIGGQLKEALLDTGADDTVLEEMNLPGKWKPKMIGGIGGFIKVRQYDQIPVEICGHKAIGTVLVGPS PVNIIGRNLLTQIGCTLNF A,B polypeptide(L) n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n n Lentivirus SF2 Escherichia sample GAG 11676 Human immunodeficiency virus 1 562 Escherichia coli TAP106 plasmid pXC35 1 2.09 41.08 VAPOR DIFFUSION, HANGING DROP 5.5 0.126 M Sodium Phosphate pH 6.2, 0.063 M Sodium Citrate, 23-24% Ammonium Sulfate, pH 5.5, VAPOR DIFFUSION, HANGING DROP, temperature 298K 298 software database_2 struct_conn struct_ref_seq_dif struct_site chem_comp_atom chem_comp_bond pdbx_initial_refinement_model repository Initial release Version format compliance Non-polymer description Version format compliance Refinement description Database references Derived calculations Data collection Refinement description 1 0 2006-11-07 1 1 2008-05-01 1 2 2011-07-13 1 3 2017-10-18 1 4 2021-10-20 1 5 2023-08-30 _database_2.pdbx_DOI _database_2.pdbx_database_accession _struct_conn.pdbx_leaving_atom_flag _struct_ref_seq_dif.details _struct_site.pdbx_auth_asym_id _struct_site.pdbx_auth_comp_id _struct_site.pdbx_auth_seq_id HETEROGEN THE ENTIRE CHAIN I IS AN INHIBITOR SAQUINAVIR. RCSB Y RCSB 2005-12-22 REL REL PO4 PHOSPHATE ION QNC quinoline-2-carboxylic acid ASN ASPARAGINE HPH (2S)-2-amino-3-phenylpropane-1,1-diol DIQ 2-METHYL-DECAHYDRO-ISOQUINOLINE-3-CARBOXYLIC ACID NTB TERTIARY-BUTYLAMINE HOH water 1F7A pdb entry 1F7A PDB experimental model PO4 501 2 PO4 PO4 501 A PO4 502 2 PO4 PO4 502 A PO4 503 2 PO4 PO4 503 A QNC 1 3 QNC QNC 504 A ASN 2 4 ASN ASN 505 A HPH 3 5 HPH HPH 506 A DIQ 4 6 DIQ DIQ 507 A NTB 5 7 NTB NTB 508 A PO4 504 2 PO4 PO4 504 B PO4 505 2 PO4 PO4 505 B WAT 4 8 HOH HOH 509 A WAT 6 8 HOH HOH 510 A WAT 8 8 HOH HOH 511 A WAT 9 8 HOH HOH 512 A WAT 11 8 HOH HOH 513 A WAT 12 8 HOH HOH 514 A WAT 25 8 HOH HOH 515 A WAT 28 8 HOH HOH 516 A WAT 33 8 HOH HOH 517 A WAT 36 8 HOH HOH 518 A WAT 39 8 HOH HOH 519 A WAT 40 8 HOH HOH 520 A WAT 41 8 HOH HOH 521 A WAT 44 8 HOH HOH 522 A WAT 47 8 HOH HOH 523 A WAT 50 8 HOH HOH 524 A WAT 56 8 HOH HOH 525 A WAT 59 8 HOH HOH 526 A WAT 65 8 HOH HOH 527 A WAT 75 8 HOH HOH 528 A WAT 79 8 HOH HOH 529 A WAT 81 8 HOH HOH 530 A WAT 82 8 HOH HOH 531 A WAT 85 8 HOH HOH 532 A WAT 89 8 HOH HOH 533 A WAT 92 8 HOH HOH 534 A WAT 99 8 HOH HOH 535 A WAT 100 8 HOH HOH 536 A WAT 104 8 HOH HOH 537 A WAT 106 8 HOH HOH 538 A WAT 109 8 HOH HOH 539 A WAT 111 8 HOH HOH 540 A WAT 112 8 HOH HOH 541 A WAT 115 8 HOH HOH 542 A WAT 116 8 HOH HOH 543 A WAT 123 8 HOH HOH 544 A WAT 125 8 HOH HOH 545 A WAT 127 8 HOH HOH 546 A WAT 128 8 HOH HOH 547 A WAT 130 8 HOH HOH 548 A WAT 131 8 HOH HOH 549 A WAT 134 8 HOH HOH 550 A WAT 137 8 HOH HOH 551 A WAT 138 8 HOH HOH 552 A WAT 143 8 HOH HOH 553 A WAT 144 8 HOH HOH 554 A WAT 153 8 HOH HOH 555 A WAT 154 8 HOH HOH 556 A WAT 160 8 HOH HOH 557 A WAT 161 8 HOH HOH 558 A WAT 163 8 HOH HOH 559 A WAT 179 8 HOH HOH 560 A WAT 181 8 HOH HOH 561 A WAT 182 8 HOH HOH 562 A WAT 183 8 HOH HOH 563 A WAT 114 8 HOH HOH 564 A WAT 185 8 HOH HOH 565 A WAT 1 8 HOH HOH 506 B WAT 2 8 HOH HOH 507 B WAT 13 8 HOH HOH 508 B WAT 14 8 HOH HOH 509 B WAT 15 8 HOH HOH 510 B WAT 23 8 HOH HOH 511 B WAT 26 8 HOH HOH 512 B WAT 27 8 HOH HOH 513 B WAT 31 8 HOH HOH 514 B WAT 32 8 HOH HOH 515 B WAT 45 8 HOH HOH 516 B WAT 49 8 HOH HOH 517 B WAT 51 8 HOH HOH 518 B WAT 52 8 HOH HOH 519 B WAT 53 8 HOH HOH 520 B WAT 61 8 HOH HOH 521 B WAT 66 8 HOH HOH 522 B WAT 67 8 HOH HOH 523 B WAT 68 8 HOH HOH 524 B WAT 69 8 HOH HOH 525 B WAT 70 8 HOH HOH 526 B WAT 71 8 HOH HOH 527 B WAT 72 8 HOH HOH 528 B WAT 76 8 HOH HOH 529 B WAT 78 8 HOH HOH 530 B WAT 80 8 HOH HOH 531 B WAT 83 8 HOH HOH 532 B WAT 84 8 HOH HOH 533 B WAT 86 8 HOH HOH 534 B WAT 90 8 HOH HOH 535 B WAT 91 8 HOH HOH 536 B WAT 93 8 HOH HOH 537 B WAT 96 8 HOH HOH 538 B WAT 97 8 HOH HOH 539 B WAT 98 8 HOH HOH 540 B WAT 101 8 HOH HOH 541 B WAT 103 8 HOH HOH 542 B WAT 107 8 HOH HOH 543 B WAT 108 8 HOH HOH 544 B WAT 110 8 HOH HOH 545 B WAT 113 8 HOH HOH 546 B WAT 118 8 HOH HOH 547 B WAT 120 8 HOH HOH 548 B WAT 121 8 HOH HOH 549 B WAT 122 8 HOH HOH 550 B WAT 126 8 HOH HOH 551 B WAT 129 8 HOH HOH 552 B WAT 132 8 HOH HOH 553 B WAT 135 8 HOH HOH 554 B WAT 136 8 HOH HOH 555 B WAT 139 8 HOH HOH 556 B WAT 141 8 HOH HOH 557 B WAT 142 8 HOH HOH 558 B WAT 145 8 HOH HOH 559 B WAT 146 8 HOH HOH 560 B WAT 147 8 HOH HOH 561 B WAT 148 8 HOH HOH 562 B WAT 149 8 HOH HOH 563 B WAT 150 8 HOH HOH 564 B WAT 152 8 HOH HOH 565 B WAT 155 8 HOH HOH 566 B WAT 156 8 HOH HOH 567 B WAT 157 8 HOH HOH 568 B WAT 159 8 HOH HOH 569 B WAT 171 8 HOH HOH 570 B WAT 172 8 HOH HOH 571 B WAT 173 8 HOH HOH 572 B WAT 174 8 HOH HOH 573 B WAT 175 8 HOH HOH 574 B WAT 176 8 HOH HOH 575 B WAT 177 8 HOH HOH 576 B WAT 178 8 HOH HOH 577 B WAT 186 8 HOH HOH 578 B PRO 1 n 1 PRO 1 A GLN 2 n 2 GLN 2 A ILE 3 n 3 ILE 3 A THR 4 n 4 THR 4 A LEU 5 n 5 LEU 5 A TRP 6 n 6 TRP 6 A LYS 7 n 7 LYS 7 A ARG 8 n 8 ARG 8 A PRO 9 n 9 PRO 9 A LEU 10 n 10 LEU 10 A VAL 11 n 11 VAL 11 A THR 12 n 12 THR 12 A ILE 13 n 13 ILE 13 A ARG 14 n 14 ARG 14 A ILE 15 n 15 ILE 15 A GLY 16 n 16 GLY 16 A GLY 17 n 17 GLY 17 A ALA 18 n 18 GLN 18 A LEU 19 n 19 LEU 19 A LYS 20 n 20 LYS 20 A GLU 21 n 21 GLU 21 A ALA 22 n 22 ALA 22 A LEU 23 n 23 LEU 23 A LEU 24 n 24 LEU 24 A ASP 25 n 25 ASP 25 A THR 26 n 26 THR 26 A GLY 27 n 27 GLY 27 A ALA 28 n 28 ALA 28 A ASP 29 n 29 ASP 29 A ASP 30 n 30 ASP 30 A THR 31 n 31 THR 31 A VAL 32 n 32 VAL 32 A LEU 33 n 33 LEU 33 A GLU 34 n 34 GLU 34 A GLU 35 n 35 GLU 35 A MET 36 n 36 MET 36 A ASN 37 n 37 ASN 37 A LEU 38 n 38 LEU 38 A PRO 39 n 39 PRO 39 A GLY 40 n 40 GLY 40 A ALA 41 n 41 LYS 41 A TRP 42 n 42 TRP 42 A ALA 43 n 43 LYS 43 A PRO 44 n 44 PRO 44 A LYS 45 n 45 LYS 45 A MET 46 n 46 MET 46 A ILE 47 n 47 ILE 47 A GLY 48 n 48 GLY 48 A GLY 49 n 49 GLY 49 A ILE 50 n 50 ILE 50 A GLY 51 n 51 GLY 51 A GLY 52 n 52 GLY 52 A PHE 53 n 53 PHE 53 A ILE 54 n 54 ILE 54 A LYS 55 n 55 LYS 55 A VAL 56 n 56 VAL 56 A ARG 57 n 57 ARG 57 A GLN 58 n 58 GLN 58 A TYR 59 n 59 TYR 59 A ASP 60 n 60 ASP 60 A GLN 61 n 61 GLN 61 A ILE 62 n 62 ILE 62 A PRO 63 n 63 PRO 63 A VAL 64 n 64 VAL 64 A GLU 65 n 65 GLU 65 A ILE 66 n 66 ILE 66 A CYS 67 n 67 CYS 67 A GLY 68 n 68 GLY 68 A HIS 69 n 69 HIS 69 A LYS 70 n 70 LYS 70 A ALA 71 n 71 ALA 71 A ILE 72 n 72 ILE 72 A GLY 73 n 73 GLY 73 A THR 74 n 74 THR 74 A VAL 75 n 75 VAL 75 A LEU 76 n 76 LEU 76 A VAL 77 n 77 VAL 77 A GLY 78 n 78 GLY 78 A PRO 79 n 79 PRO 79 A SER 80 n 80 SER 80 A PRO 81 n 81 PRO 81 A VAL 82 n 82 VAL 82 A ASN 83 n 83 ASN 83 A ILE 84 n 84 ILE 84 A ILE 85 n 85 ILE 85 A GLY 86 n 86 GLY 86 A ARG 87 n 87 ARG 87 A ASN 88 n 88 ASN 88 A LEU 89 n 89 LEU 89 A LEU 90 n 90 LEU 90 A THR 91 n 91 THR 91 A GLN 92 n 92 GLN 92 A ILE 93 n 93 ILE 93 A GLY 94 n 94 GLY 94 A CYS 95 n 95 CYS 95 A THR 96 n 96 THR 96 A LEU 97 n 97 LEU 97 A ASN 98 n 98 ASN 98 A PHE 99 n 99 PHE 99 A PRO 1 n 1 PRO 1 B GLN 2 n 2 GLN 2 B ILE 3 n 3 ILE 3 B THR 4 n 4 THR 4 B LEU 5 n 5 LEU 5 B TRP 6 n 6 TRP 6 B ALA 7 n 7 LYS 7 B ARG 8 n 8 ARG 8 B PRO 9 n 9 PRO 9 B LEU 10 n 10 LEU 10 B VAL 11 n 11 VAL 11 B THR 12 n 12 THR 12 B ILE 13 n 13 ILE 13 B ALA 14 n 14 ARG 14 B ILE 15 n 15 ILE 15 B GLY 16 n 16 GLY 16 B GLY 17 n 17 GLY 17 B ALA 18 n 18 GLN 18 B LEU 19 n 19 LEU 19 B LYS 20 n 20 LYS 20 B ALA 21 n 21 GLU 21 B ALA 22 n 22 ALA 22 B LEU 23 n 23 LEU 23 B LEU 24 n 24 LEU 24 B ASP 25 n 25 ASP 25 B THR 26 n 26 THR 26 B GLY 27 n 27 GLY 27 B ALA 28 n 28 ALA 28 B ASP 29 n 29 ASP 29 B ASP 30 n 30 ASP 30 B THR 31 n 31 THR 31 B VAL 32 n 32 VAL 32 B LEU 33 n 33 LEU 33 B GLU 34 n 34 GLU 34 B GLU 35 n 35 GLU 35 B MET 36 n 36 MET 36 B ASN 37 n 37 ASN 37 B LEU 38 n 38 LEU 38 B PRO 39 n 39 PRO 39 B GLY 40 n 40 GLY 40 B ALA 41 n 41 LYS 41 B TRP 42 n 42 TRP 42 B ALA 43 n 43 LYS 43 B PRO 44 n 44 PRO 44 B ALA 45 n 45 LYS 45 B MET 46 n 46 MET 46 B ILE 47 n 47 ILE 47 B GLY 48 n 48 GLY 48 B GLY 49 n 49 GLY 49 B ILE 50 n 50 ILE 50 B GLY 51 n 51 GLY 51 B GLY 52 n 52 GLY 52 B PHE 53 n 53 PHE 53 B ILE 54 n 54 ILE 54 B LYS 55 n 55 LYS 55 B VAL 56 n 56 VAL 56 B ALA 57 n 57 ARG 57 B GLN 58 n 58 GLN 58 B TYR 59 n 59 TYR 59 B ASP 60 n 60 ASP 60 B GLN 61 n 61 GLN 61 B ILE 62 n 62 ILE 62 B PRO 63 n 63 PRO 63 B VAL 64 n 64 VAL 64 B GLU 65 n 65 GLU 65 B ILE 66 n 66 ILE 66 B CYS 67 n 67 CYS 67 B GLY 68 n 68 GLY 68 B HIS 69 n 69 HIS 69 B ALA 70 n 70 LYS 70 B ALA 71 n 71 ALA 71 B ILE 72 n 72 ILE 72 B GLY 73 n 73 GLY 73 B THR 74 n 74 THR 74 B VAL 75 n 75 VAL 75 B LEU 76 n 76 LEU 76 B VAL 77 n 77 VAL 77 B GLY 78 n 78 GLY 78 B PRO 79 n 79 PRO 79 B SER 80 n 80 SER 80 B PRO 81 n 81 PRO 81 B VAL 82 n 82 VAL 82 B ASN 83 n 83 ASN 83 B ILE 84 n 84 ILE 84 B ILE 85 n 85 ILE 85 B GLY 86 n 86 GLY 86 B ARG 87 n 87 ARG 87 B ASN 88 n 88 ASN 88 B LEU 89 n 89 LEU 89 B LEU 90 n 90 LEU 90 B THR 91 n 91 THR 91 B GLN 92 n 92 GLN 92 B ILE 93 n 93 ILE 93 B GLY 94 n 94 GLY 94 B CYS 95 n 95 CYS 95 B THR 96 n 96 THR 96 B LEU 97 n 97 LEU 97 B ASN 98 n 98 ASN 98 B PHE 99 n 99 PHE 99 B author_and_software_defined_assembly PISA 2 dimeric 6120 -36 9030 1.0000000000 0.0000000000 0.0000000000 0.0000000000 1.0000000000 0.0000000000 0.0000000000 0.0000000000 1.0000000000 1_555 x,y,z identity operation 0.0000000000 0.0000000000 0.0000000000 A N ILE 3 A N ILE 3 B O LEU 97 B O LEU 97 B O ASN 98 B O ASN 98 A N THR 96 A N THR 96 A N LEU 97 A N LEU 97 B O ILE 3 B O ILE 3 A N LYS 45 A N LYS 45 A O VAL 56 A O VAL 56 A N ILE 66 A N ILE 66 A O HIS 69 A O HIS 69 A O LEU 76 A O LEU 76 A N LEU 33 A N LEU 33 A N VAL 32 A N VAL 32 A O ILE 84 A O ILE 84 A O ILE 85 A O ILE 85 A N LEU 23 A N LEU 23 A O LYS 20 A O LYS 20 A N ILE 13 A N ILE 13 A N ARG 14 A N ARG 14 A O GLU 65 A O GLU 65 B N LYS 45 B N LYS 45 B O VAL 56 B O VAL 56 B N ILE 66 B N ILE 66 B O HIS 69 B O HIS 69 B O LEU 76 B O LEU 76 B N LEU 33 B N LEU 33 B N VAL 32 B N VAL 32 B O ILE 84 B O ILE 84 B O ILE 85 B O ILE 85 B N LEU 23 B N LEU 23 B O LYS 20 B O LYS 20 B N ILE 13 B N ILE 13 B N ARG 14 B N ARG 14 B O GLU 65 B O GLU 65 1 A CG GLN 18 A CG GLN 18 1 Y 1 A CD GLN 18 A CD GLN 18 1 Y 1 A OE1 GLN 18 A OE1 GLN 18 1 Y 1 A NE2 GLN 18 A NE2 GLN 18 1 Y 1 A CG LYS 41 A CG LYS 41 1 Y 1 A CD LYS 41 A CD LYS 41 1 Y 1 A CE LYS 41 A CE LYS 41 1 Y 1 A NZ LYS 41 A NZ LYS 41 1 Y 1 A CG LYS 43 A CG LYS 43 1 Y 1 A CD LYS 43 A CD LYS 43 1 Y 1 A CE LYS 43 A CE LYS 43 1 Y 1 A NZ LYS 43 A NZ LYS 43 1 Y 1 B CG LYS 7 B CG LYS 7 1 Y 1 B CD LYS 7 B CD LYS 7 1 Y 1 B CE LYS 7 B CE LYS 7 1 Y 1 B NZ LYS 7 B NZ LYS 7 1 Y 1 B CG ARG 14 B CG ARG 14 1 Y 1 B CD ARG 14 B CD ARG 14 1 Y 1 B NE ARG 14 B NE ARG 14 1 Y 1 B CZ ARG 14 B CZ ARG 14 1 Y 1 B NH1 ARG 14 B NH1 ARG 14 1 Y 1 B NH2 ARG 14 B NH2 ARG 14 1 Y 1 B CG GLN 18 B CG GLN 18 1 Y 1 B CD GLN 18 B CD GLN 18 1 Y 1 B OE1 GLN 18 B OE1 GLN 18 1 Y 1 B NE2 GLN 18 B NE2 GLN 18 1 Y 1 B CG GLU 21 B CG GLU 21 1 Y 1 B CD GLU 21 B CD GLU 21 1 Y 1 B OE1 GLU 21 B OE1 GLU 21 1 Y 1 B OE2 GLU 21 B OE2 GLU 21 1 Y 1 B CG LYS 41 B CG LYS 41 1 Y 1 B CD LYS 41 B CD LYS 41 1 Y 1 B CE LYS 41 B CE LYS 41 1 Y 1 B NZ LYS 41 B NZ LYS 41 1 Y 1 B CG LYS 43 B CG LYS 43 1 Y 1 B CD LYS 43 B CD LYS 43 1 Y 1 B CE LYS 43 B CE LYS 43 1 Y 1 B NZ LYS 43 B NZ LYS 43 1 Y 1 B CG LYS 45 B CG LYS 45 1 Y 1 B CD LYS 45 B CD LYS 45 1 Y 1 B CE LYS 45 B CE LYS 45 1 Y 1 B NZ LYS 45 B NZ LYS 45 1 Y 1 B CG ARG 57 B CG ARG 57 1 Y 1 B CD ARG 57 B CD ARG 57 1 Y 1 B NE ARG 57 B NE ARG 57 1 Y 1 B CZ ARG 57 B CZ ARG 57 1 Y 1 B NH1 ARG 57 B NH1 ARG 57 1 Y 1 B NH2 ARG 57 B NH2 ARG 57 1 Y 1 B CG LYS 70 B CG LYS 70 1 Y 1 B CD LYS 70 B CD LYS 70 1 Y 1 B CE LYS 70 B CE LYS 70 1 Y 1 B NZ LYS 70 B NZ LYS 70 1 Y 1 A A O N QNC ASN 504 505 2.08 21.948 -0.73 0.00 0.00 0.52 0.00 0.21 0.957 0.930 HYDROGENS HAVE BEEN ADDED IN THE RIDING POSITIONS 0.23235 0.1764 0.1791 0.17911 2.00 42.22 612 12625 11977 4.9 99.09 4.559 0.127 RANDOM 1 Isotropic THROUGHOUT 0 0 MOLECULAR REPLACEMENT 0.205 0.178 0.80 0.80 1.20 pdb entry 1F7A MAXIMUM LIKELIHOOD BABINET MODEL WITH MASK 2.00 42.22 130 1666 74 0 1462 0.008 0.022 1589 0.000 0.020 1518 1.613 2.027 2178 0.679 3.000 3519 6.942 5.000 200 42.207 25.000 50 12.644 15.000 245 27.859 15.000 6 0.093 0.200 256 0.004 0.020 1719 0.001 0.020 285 0.199 0.300 231 0.213 0.300 1461 0.176 0.500 757 0.092 0.500 954 0.190 0.500 153 0.073 0.500 1 0.062 0.300 11 0.177 0.300 77 0.216 0.500 22 1.200 1.500 1259 0.263 1.500 416 1.443 2.000 1601 2.217 3.000 711 3.321 4.500 577 0.331 0.235 2.052 47 783 20 90.91 2.0 42.22 2FGU 12625 12625 0 0 0.073 0.073 1 8.2 7.0 99.1 refinement REFMAC 5.2.0005 data scaling SCALEPACK phasing AMoRE X-ray crystal structure of HIV-1 Protease T80S variant in complex with the inhibitor saquinavir used to explore the role of invariant Thr80 in HIV-1 protease structure, function, and viral infectivity. 1 N N 1 N N 2 N N 2 N N 2 N N 3 N N 4 N N 5 N N 6 N N 7 N N 2 N N 2 N N 8 N N 8 N N The entire HIV-1 protease dimer in complex with the inhibitor saquinavir. A GLY 86 A GLY 86 HELX_P A THR 91 A THR 91 1 1 6 B GLY 86 B GLY 86 HELX_P B THR 91 B THR 91 1 2 6 covale 1.336 both A QNC 504 F C QNC 1_555 A ASN 505 G N ASN 1_555 covale 1.346 one A ASN 505 G C ASN 1_555 A HPH 506 H N HPH 1_555 covale 1.345 none A HPH 506 H C HPH 1_555 A DIQ 507 I CM DIQ 1_555 covale 1.345 one A DIQ 507 I C DIQ 1_555 A NTB 508 J N NTB 1_555 HYDROLASE HIV Protease, drug resistance, enzyme kinetics, sequence conservation, protein structure, HYDROLASE O38716_9HIV1 UNP 1 1 O38716 1 99 2FGU 1 99 O38716 A 1 1 99 1 99 2FGU 1 99 O38716 B 1 1 99 1 GLN engineered mutation LYS 7 2FGU A O38716 UNP 7 7 1 ILE engineered mutation VAL 64 2FGU A O38716 UNP 64 64 1 THR engineered mutation SER 80 2FGU A O38716 UNP 80 80 2 GLN engineered mutation LYS 7 2FGU B O38716 UNP 7 7 2 ILE engineered mutation VAL 64 2FGU B O38716 UNP 64 64 2 THR engineered mutation SER 80 2FGU B O38716 UNP 80 80 4 8 8 anti-parallel anti-parallel anti-parallel anti-parallel anti-parallel parallel anti-parallel parallel anti-parallel anti-parallel anti-parallel anti-parallel parallel anti-parallel parallel anti-parallel anti-parallel A GLN 2 A GLN 2 A ILE 3 A ILE 3 B THR 96 B THR 96 B ASN 98 B ASN 98 A THR 96 A THR 96 A ASN 98 A ASN 98 B GLN 2 B GLN 2 B ILE 3 B ILE 3 A LYS 43 A LYS 43 A GLY 49 A GLY 49 A GLY 52 A GLY 52 A ILE 66 A ILE 66 A HIS 69 A HIS 69 A VAL 77 A VAL 77 A VAL 32 A VAL 32 A LEU 33 A LEU 33 A ASN 83 A ASN 83 A ILE 85 A ILE 85 A GLN 18 A GLN 18 A LEU 24 A LEU 24 A LEU 10 A LEU 10 A ILE 15 A ILE 15 A GLY 52 A GLY 52 A ILE 66 A ILE 66 B LYS 43 B LYS 43 B GLY 49 B GLY 49 B GLY 52 B GLY 52 B ILE 66 B ILE 66 B HIS 69 B HIS 69 B VAL 77 B VAL 77 B VAL 32 B VAL 32 B LEU 33 B LEU 33 B ILE 84 B ILE 84 B ILE 85 B ILE 85 B GLN 18 B GLN 18 B LEU 24 B LEU 24 B LEU 10 B LEU 10 B ILE 15 B ILE 15 B GLY 52 B GLY 52 B ILE 66 B ILE 66 BINDING SITE FOR RESIDUE PO4 A 501 A PO4 501 Software 6 BINDING SITE FOR RESIDUE PO4 A 502 A PO4 502 Software 5 BINDING SITE FOR RESIDUE PO4 A 503 A PO4 503 Software 7 BINDING SITE FOR RESIDUE PO4 B 504 B PO4 504 Software 5 BINDING SITE FOR RESIDUE PO4 B 505 B PO4 505 Software 5 BINDING SITE FOR RESIDUE QNC A 504 A QNC 504 Software 10 BINDING SITE FOR RESIDUE ASN A 505 A ASN 505 Software 9 BINDING SITE FOR RESIDUE HPH A 506 A HPH 506 Software 10 BINDING SITE FOR RESIDUE DIQ A 507 A DIQ 507 Software 8 BINDING SITE FOR RESIDUE NTB A 508 A NTB 508 Software 4 A ARG 14 A ARG 14 6 1_555 A GLY 17 A GLY 17 6 1_555 A PRO 63 A PRO 63 6 1_555 A HOH 522 M HOH 6 1_555 A HOH 529 M HOH 6 1_555 B HOH 544 N HOH 6 1_455 A GLY 73 A GLY 73 5 1_555 A THR 74 A THR 74 5 1_555 A ASN 88 A ASN 88 5 1_555 A GLN 92 A GLN 92 5 1_555 A HOH 565 M HOH 5 1_555 A PRO 1 A PRO 1 7 1_555 A LYS 55 A LYS 55 7 2_554 B HIS 69 B HIS 69 7 4_455 B LYS 70 B LYS 70 7 4_455 B PHE 99 B PHE 99 7 1_555 B HOH 563 N HOH 7 4_455 B HOH 577 N HOH 7 4_455 A PRO 39 A PRO 39 5 1_655 A GLY 40 A GLY 40 5 1_655 B MET 36 B MET 36 5 1_555 B ASN 37 B ASN 37 5 1_555 B HOH 549 N HOH 5 1_555 B LYS 20 B LYS 20 5 1_555 B GLU 21 B GLU 21 5 1_555 B ASN 83 B ASN 83 5 1_555 B HOH 528 N HOH 5 1_555 B HOH 542 N HOH 5 1_555 A TRP 6 A TRP 6 10 3_645 A GLY 27 A GLY 27 10 1_555 A ALA 28 A ALA 28 10 1_555 A ASP 29 A ASP 29 10 1_555 A GLY 48 A GLY 48 10 1_555 A ASN 505 G ASN 10 1_555 A HPH 506 H HPH 10 1_555 A HOH 524 M HOH 10 1_555 B ARG 8 B ARG 8 10 1_555 B PRO 81 B PRO 81 10 1_555 A ALA 28 A ALA 28 9 1_555 A ASP 29 A ASP 29 9 1_555 A ASP 30 A ASP 30 9 1_555 A GLY 48 A GLY 48 9 1_555 A QNC 504 F QNC 9 1_555 A HPH 506 H HPH 9 1_555 A HOH 510 M HOH 9 1_555 A HOH 530 M HOH 9 1_555 B ILE 50 B ILE 50 9 1_555 A ASP 25 A ASP 25 10 1_555 A GLY 27 A GLY 27 10 1_555 A GLY 49 A GLY 49 10 1_555 A ILE 50 A ILE 50 10 1_555 A QNC 504 F QNC 10 1_555 A ASN 505 G ASN 10 1_555 A DIQ 507 I DIQ 10 1_555 B ASP 25 B ASP 25 10 1_555 B PRO 81 B PRO 81 10 1_555 B ILE 84 B ILE 84 10 1_555 A ASP 25 A ASP 25 8 1_555 A PRO 81 A PRO 81 8 1_555 A ILE 84 A ILE 84 8 1_555 A HPH 506 H HPH 8 1_555 A NTB 508 J NTB 8 1_555 A HOH 510 M HOH 8 1_555 B ASP 25 B ASP 25 8 1_555 B GLY 27 B GLY 27 8 1_555 A DIQ 507 I DIQ 4 1_555 A HOH 518 M HOH 4 1_555 B ALA 28 B ALA 28 4 1_555 B GLY 48 B GLY 48 4 1_555 19 P 21 21 21