HEADER STRUCTURAL GENOMICS, UNKNOWN FUNCTION 30-MAY-04 1WK2 TITLE CRYSTAL STRUCTURE OF A HYPOTHETICAL PROTEIN FROM THERMUS THERMOPHILUS TITLE 2 HB8 COMPND MOL_ID: 1; COMPND 2 MOLECULE: HYPOTHETICAL PROTEIN; COMPND 3 CHAIN: A; COMPND 4 ENGINEERED: YES SOURCE MOL_ID: 1; SOURCE 2 ORGANISM_SCIENTIFIC: THERMUS THERMOPHILUS; SOURCE 3 ORGANISM_TAXID: 274; SOURCE 4 EXPRESSION_SYSTEM: ESCHERICHIA COLI; SOURCE 5 EXPRESSION_SYSTEM_TAXID: 562; SOURCE 6 EXPRESSION_SYSTEM_STRAIN: B834(DE3); SOURCE 7 EXPRESSION_SYSTEM_VECTOR_TYPE: PLASMID; SOURCE 8 EXPRESSION_SYSTEM_PLASMID: PET11A KEYWDS STRUCTURAL GENOMICS, RIKEN STRUCTURAL GENOMICS/PROTEOMICS INITIATIVE, KEYWDS 2 RSGI, UNKNOWN FUNCTION EXPDTA X-RAY DIFFRACTION AUTHOR Y.AGARI,S.YOKOYAMA,S.KURAMITSU,RIKEN STRUCTURAL GENOMICS/PROTEOMICS AUTHOR 2 INITIATIVE (RSGI) REVDAT 4 16-OCT-24 1WK2 1 LINK REVDAT 3 13-JUL-11 1WK2 1 VERSN REVDAT 2 24-FEB-09 1WK2 1 VERSN REVDAT 1 30-NOV-04 1WK2 0 JRNL AUTH Y.AGARI,S.YOKOYAMA,S.KURAMITSU JRNL TITL CRYSTAL STRUCTURE OF A HYPOTHETICAL PROTEIN FROM THERMUS JRNL TITL 2 THERMOPHILUS HB8 JRNL REF TO BE PUBLISHED JRNL REFN REMARK 2 REMARK 2 RESOLUTION. 2.50 ANGSTROMS. REMARK 3 REMARK 3 REFINEMENT. REMARK 3 PROGRAM : CNS 1.1 REMARK 3 AUTHORS : BRUNGER,ADAMS,CLORE,DELANO,GROS,GROSSE- REMARK 3 : KUNSTLEVE,JIANG,KUSZEWSKI,NILGES,PANNU, REMARK 3 : READ,RICE,SIMONSON,WARREN REMARK 3 REMARK 3 REFINEMENT TARGET : NULL REMARK 3 REMARK 3 DATA USED IN REFINEMENT. REMARK 3 RESOLUTION RANGE HIGH (ANGSTROMS) : 2.50 REMARK 3 RESOLUTION RANGE LOW (ANGSTROMS) : 29.78 REMARK 3 DATA CUTOFF (SIGMA(F)) : 0.000 REMARK 3 DATA CUTOFF HIGH (ABS(F)) : 1159702.070 REMARK 3 DATA CUTOFF LOW (ABS(F)) : 0.0000 REMARK 3 COMPLETENESS (WORKING+TEST) (%) : 97.6 REMARK 3 NUMBER OF REFLECTIONS : 4268 REMARK 3 REMARK 3 FIT TO DATA USED IN REFINEMENT. REMARK 3 CROSS-VALIDATION METHOD : THROUGHOUT REMARK 3 FREE R VALUE TEST SET SELECTION : RANDOM REMARK 3 R VALUE (WORKING SET) : 0.327 REMARK 3 FREE R VALUE : 0.389 REMARK 3 FREE R VALUE TEST SET SIZE (%) : 10.600 REMARK 3 FREE R VALUE TEST SET COUNT : 451 REMARK 3 ESTIMATED ERROR OF FREE R VALUE : 0.018 REMARK 3 REMARK 3 FIT IN THE HIGHEST RESOLUTION BIN. REMARK 3 TOTAL NUMBER OF BINS USED : 6 REMARK 3 BIN RESOLUTION RANGE HIGH (A) : 2.50 REMARK 3 BIN RESOLUTION RANGE LOW (A) : 2.66 REMARK 3 BIN COMPLETENESS (WORKING+TEST) (%) : 99.90 REMARK 3 REFLECTIONS IN BIN (WORKING SET) : 650 REMARK 3 BIN R VALUE (WORKING SET) : 0.3730 REMARK 3 BIN FREE R VALUE : 0.4630 REMARK 3 BIN FREE R VALUE TEST SET SIZE (%) : 10.60 REMARK 3 BIN FREE R VALUE TEST SET COUNT : 77 REMARK 3 ESTIMATED ERROR OF BIN FREE R VALUE : 0.053 REMARK 3 REMARK 3 NUMBER OF NON-HYDROGEN ATOMS USED IN REFINEMENT. REMARK 3 PROTEIN ATOMS : 683 REMARK 3 NUCLEIC ACID ATOMS : 0 REMARK 3 HETEROGEN ATOMS : 0 REMARK 3 SOLVENT ATOMS : 45 REMARK 3 REMARK 3 B VALUES. REMARK 3 FROM WILSON PLOT (A**2) : 30.10 REMARK 3 MEAN B VALUE (OVERALL, A**2) : 26.20 REMARK 3 OVERALL ANISOTROPIC B VALUE. REMARK 3 B11 (A**2) : -9.01000 REMARK 3 B22 (A**2) : 11.81000 REMARK 3 B33 (A**2) : -2.80000 REMARK 3 B12 (A**2) : 0.00000 REMARK 3 B13 (A**2) : 1.27000 REMARK 3 B23 (A**2) : 0.00000 REMARK 3 REMARK 3 ESTIMATED COORDINATE ERROR. REMARK 3 ESD FROM LUZZATI PLOT (A) : 0.48 REMARK 3 ESD FROM SIGMAA (A) : 0.33 REMARK 3 LOW RESOLUTION CUTOFF (A) : 5.00 REMARK 3 REMARK 3 CROSS-VALIDATED ESTIMATED COORDINATE ERROR. REMARK 3 ESD FROM C-V LUZZATI PLOT (A) : 0.56 REMARK 3 ESD FROM C-V SIGMAA (A) : 0.52 REMARK 3 REMARK 3 RMS DEVIATIONS FROM IDEAL VALUES. REMARK 3 BOND LENGTHS (A) : 0.008 REMARK 3 BOND ANGLES (DEGREES) : 1.500 REMARK 3 DIHEDRAL ANGLES (DEGREES) : 25.70 REMARK 3 IMPROPER ANGLES (DEGREES) : 0.900 REMARK 3 REMARK 3 ISOTROPIC THERMAL MODEL : RESTRAINED REMARK 3 REMARK 3 ISOTROPIC THERMAL FACTOR RESTRAINTS. RMS SIGMA REMARK 3 MAIN-CHAIN BOND (A**2) : 0.000 ; 1.500 REMARK 3 MAIN-CHAIN ANGLE (A**2) : 0.000 ; 2.000 REMARK 3 SIDE-CHAIN BOND (A**2) : 0.000 ; 2.000 REMARK 3 SIDE-CHAIN ANGLE (A**2) : 0.000 ; 2.500 REMARK 3 REMARK 3 BULK SOLVENT MODELING. REMARK 3 METHOD USED : FLAT MODEL REMARK 3 KSOL : 0.44 REMARK 3 BSOL : 58.03 REMARK 3 REMARK 3 NCS MODEL : NULL REMARK 3 REMARK 3 NCS RESTRAINTS. RMS SIGMA/WEIGHT REMARK 3 GROUP 1 POSITIONAL (A) : NULL ; NULL REMARK 3 GROUP 1 B-FACTOR (A**2) : NULL ; NULL REMARK 3 REMARK 3 PARAMETER FILE 1 : PROTEIN_REP.PARAM REMARK 3 PARAMETER FILE 2 : WATER_REP.PARAM REMARK 3 PARAMETER FILE 3 : NULL REMARK 3 TOPOLOGY FILE 1 : PROTEIN.TOP REMARK 3 TOPOLOGY FILE 2 : WATER.TOP REMARK 3 TOPOLOGY FILE 3 : NULL REMARK 3 REMARK 3 OTHER REFINEMENT REMARKS: BULK SOLVENT MODEL USED REMARK 4 REMARK 4 1WK2 COMPLIES WITH FORMAT V. 3.30, 13-JUL-11 REMARK 100 REMARK 100 THIS ENTRY HAS BEEN PROCESSED BY PDBJ ON 28-JUN-04. REMARK 100 THE DEPOSITION ID IS D_1000023662. REMARK 200 REMARK 200 EXPERIMENTAL DETAILS REMARK 200 EXPERIMENT TYPE : X-RAY DIFFRACTION REMARK 200 DATE OF DATA COLLECTION : 17-APR-04; NULL; NULL REMARK 200 TEMPERATURE (KELVIN) : 100; NULL; NULL REMARK 200 PH : 6.7 REMARK 200 NUMBER OF CRYSTALS USED : 1 REMARK 200 REMARK 200 SYNCHROTRON (Y/N) : Y; NULL; NULL REMARK 200 RADIATION SOURCE : SPRING-8; NULL; NULL REMARK 200 BEAMLINE : BL26B2; NULL; NULL REMARK 200 X-RAY GENERATOR MODEL : NULL; NULL; NULL REMARK 200 MONOCHROMATIC OR LAUE (M/L) : M; M; M REMARK 200 WAVELENGTH OR RANGE (A) : 0.97913, 0.9, 0.97942; NULL; REMARK 200 NULL REMARK 200 MONOCHROMATOR : SI DOUBLE CRYSTAL; SI DOUBLE REMARK 200 CRYSTAL; SI DOUBLE CRYSTAL REMARK 200 OPTICS : NULL; NULL; NULL REMARK 200 REMARK 200 DETECTOR TYPE : CCD; NULL; NULL REMARK 200 DETECTOR MANUFACTURER : RIGAKU JUPITER 210; NULL; NULL REMARK 200 INTENSITY-INTEGRATION SOFTWARE : HKL-2000 REMARK 200 DATA SCALING SOFTWARE : SCALEPACK REMARK 200 REMARK 200 NUMBER OF UNIQUE REFLECTIONS : NULL REMARK 200 RESOLUTION RANGE HIGH (A) : 1.900 REMARK 200 RESOLUTION RANGE LOW (A) : 43.000 REMARK 200 REJECTION CRITERIA (SIGMA(I)) : NULL REMARK 200 REMARK 200 OVERALL. REMARK 200 COMPLETENESS FOR RANGE (%) : NULL REMARK 200 DATA REDUNDANCY : NULL REMARK 200 R MERGE (I) : NULL REMARK 200 R SYM (I) : NULL REMARK 200 FOR THE DATA SET : NULL REMARK 200 REMARK 200 IN THE HIGHEST RESOLUTION SHELL. REMARK 200 HIGHEST RESOLUTION SHELL, RANGE HIGH (A) : NULL REMARK 200 HIGHEST RESOLUTION SHELL, RANGE LOW (A) : NULL REMARK 200 COMPLETENESS FOR SHELL (%) : NULL REMARK 200 DATA REDUNDANCY IN SHELL : NULL REMARK 200 R MERGE FOR SHELL (I) : NULL REMARK 200 R SYM FOR SHELL (I) : NULL REMARK 200 FOR SHELL : NULL REMARK 200 REMARK 200 DIFFRACTION PROTOCOL: MAD; MAD; MAD REMARK 200 METHOD USED TO DETERMINE THE STRUCTURE: MAD REMARK 200 SOFTWARE USED: SOLVE REMARK 200 STARTING MODEL: NULL REMARK 200 REMARK 200 REMARK: NULL REMARK 280 REMARK 280 CRYSTAL REMARK 280 SOLVENT CONTENT, VS (%): 44.80 REMARK 280 MATTHEWS COEFFICIENT, VM (ANGSTROMS**3/DA): 2.20 REMARK 280 REMARK 280 CRYSTALLIZATION CONDITIONS: 23% PEG3350, PH 6.7, VAPOR DIFFUSION, REMARK 280 HANGING DROP, TEMPERATURE 293K REMARK 290 REMARK 290 CRYSTALLOGRAPHIC SYMMETRY REMARK 290 SYMMETRY OPERATORS FOR SPACE GROUP: C 1 2 1 REMARK 290 REMARK 290 SYMOP SYMMETRY REMARK 290 NNNMMM OPERATOR REMARK 290 1555 X,Y,Z REMARK 290 2555 -X,Y,-Z REMARK 290 3555 X+1/2,Y+1/2,Z REMARK 290 4555 -X+1/2,Y+1/2,-Z REMARK 290 REMARK 290 WHERE NNN -> OPERATOR NUMBER REMARK 290 MMM -> TRANSLATION VECTOR REMARK 290 REMARK 290 CRYSTALLOGRAPHIC SYMMETRY TRANSFORMATIONS REMARK 290 THE FOLLOWING TRANSFORMATIONS OPERATE ON THE ATOM/HETATM REMARK 290 RECORDS IN THIS ENTRY TO PRODUCE CRYSTALLOGRAPHICALLY REMARK 290 RELATED MOLECULES. REMARK 290 SMTRY1 1 1.000000 0.000000 0.000000 0.00000 REMARK 290 SMTRY2 1 0.000000 1.000000 0.000000 0.00000 REMARK 290 SMTRY3 1 0.000000 0.000000 1.000000 0.00000 REMARK 290 SMTRY1 2 -1.000000 0.000000 0.000000 0.00000 REMARK 290 SMTRY2 2 0.000000 1.000000 0.000000 0.00000 REMARK 290 SMTRY3 2 0.000000 0.000000 -1.000000 0.00000 REMARK 290 SMTRY1 3 1.000000 0.000000 0.000000 26.29150 REMARK 290 SMTRY2 3 0.000000 1.000000 0.000000 27.92300 REMARK 290 SMTRY3 3 0.000000 0.000000 1.000000 0.00000 REMARK 290 SMTRY1 4 -1.000000 0.000000 0.000000 26.29150 REMARK 290 SMTRY2 4 0.000000 1.000000 0.000000 27.92300 REMARK 290 SMTRY3 4 0.000000 0.000000 -1.000000 0.00000 REMARK 290 REMARK 290 REMARK: NULL REMARK 300 REMARK 300 BIOMOLECULE: 1, 2 REMARK 300 SEE REMARK 350 FOR THE AUTHOR PROVIDED AND/OR PROGRAM REMARK 300 GENERATED ASSEMBLY INFORMATION FOR THE STRUCTURE IN REMARK 300 THIS ENTRY. THE REMARK MAY ALSO PROVIDE INFORMATION ON REMARK 300 BURIED SURFACE AREA. REMARK 350 REMARK 350 COORDINATES FOR A COMPLETE MULTIMER REPRESENTING THE KNOWN REMARK 350 BIOLOGICALLY SIGNIFICANT OLIGOMERIZATION STATE OF THE REMARK 350 MOLECULE CAN BE GENERATED BY APPLYING BIOMT TRANSFORMATIONS REMARK 350 GIVEN BELOW. BOTH NON-CRYSTALLOGRAPHIC AND REMARK 350 CRYSTALLOGRAPHIC OPERATIONS ARE GIVEN. REMARK 350 REMARK 350 BIOMOLECULE: 1 REMARK 350 AUTHOR DETERMINED BIOLOGICAL UNIT: MONOMERIC REMARK 350 APPLY THE FOLLOWING TO CHAINS: A REMARK 350 BIOMT1 1 1.000000 0.000000 0.000000 0.00000 REMARK 350 BIOMT2 1 0.000000 1.000000 0.000000 0.00000 REMARK 350 BIOMT3 1 0.000000 0.000000 1.000000 0.00000 REMARK 350 REMARK 350 BIOMOLECULE: 2 REMARK 350 SOFTWARE DETERMINED QUATERNARY STRUCTURE: DIMERIC REMARK 350 SOFTWARE USED: PISA,PQS REMARK 350 TOTAL BURIED SURFACE AREA: 2310 ANGSTROM**2 REMARK 350 SURFACE AREA OF THE COMPLEX: 10150 ANGSTROM**2 REMARK 350 CHANGE IN SOLVENT FREE ENERGY: -23.0 KCAL/MOL REMARK 350 APPLY THE FOLLOWING TO CHAINS: A REMARK 350 BIOMT1 1 1.000000 0.000000 0.000000 0.00000 REMARK 350 BIOMT2 1 0.000000 1.000000 0.000000 0.00000 REMARK 350 BIOMT3 1 0.000000 0.000000 1.000000 0.00000 REMARK 350 BIOMT1 2 -1.000000 0.000000 0.000000 52.58300 REMARK 350 BIOMT2 2 0.000000 1.000000 0.000000 0.00000 REMARK 350 BIOMT3 2 0.000000 0.000000 -1.000000 0.00000 REMARK 465 REMARK 465 MISSING RESIDUES REMARK 465 THE FOLLOWING RESIDUES WERE NOT LOCATED IN THE REMARK 465 EXPERIMENT. (M=MODEL NUMBER; RES=RESIDUE NAME; C=CHAIN REMARK 465 IDENTIFIER; SSSEQ=SEQUENCE NUMBER; I=INSERTION CODE.) REMARK 465 REMARK 465 M RES C SSSEQI REMARK 465 GLU A 56 REMARK 465 GLY A 57 REMARK 465 PRO A 58 REMARK 465 PHE A 59 REMARK 465 SER A 60 REMARK 465 VAL A 61 REMARK 465 GLU A 62 REMARK 465 GLU A 63 REMARK 465 LEU A 64 REMARK 465 LEU A 65 REMARK 465 ALA A 66 REMARK 465 HIS A 67 REMARK 465 GLN A 68 REMARK 465 GLU A 69 REMARK 465 LYS A 70 REMARK 465 HIS A 71 REMARK 465 LEU A 72 REMARK 465 ALA A 73 REMARK 465 GLU A 74 REMARK 465 GLU A 75 REMARK 465 ALA A 76 REMARK 465 PHE A 77 REMARK 465 LEU A 78 REMARK 465 ARG A 79 REMARK 465 ALA A 80 REMARK 465 TYR A 81 REMARK 465 ALA A 82 REMARK 465 LYS A 83 REMARK 465 ASP A 84 REMARK 465 GLU A 85 REMARK 465 ARG A 106 REMARK 465 ARG A 107 REMARK 465 PRO A 108 REMARK 465 GLY A 109 REMARK 465 ARG A 110 REMARK 465 VAL A 111 REMARK 465 TRP A 121 REMARK 500 REMARK 500 GEOMETRY AND STEREOCHEMISTRY REMARK 500 SUBTOPIC: CLOSE CONTACTS REMARK 500 REMARK 500 THE FOLLOWING ATOMS THAT ARE RELATED BY CRYSTALLOGRAPHIC REMARK 500 SYMMETRY ARE IN CLOSE CONTACT. AN ATOM LOCATED WITHIN 0.15 REMARK 500 ANGSTROMS OF A SYMMETRY RELATED ATOM IS ASSUMED TO BE ON A REMARK 500 SPECIAL POSITION AND IS, THEREFORE, LISTED IN REMARK 375 REMARK 500 INSTEAD OF REMARK 500. ATOMS WITH NON-BLANK ALTERNATE REMARK 500 LOCATION INDICATORS ARE NOT INCLUDED IN THE CALCULATIONS. REMARK 500 REMARK 500 DISTANCE CUTOFF: REMARK 500 2.2 ANGSTROMS FOR CONTACTS NOT INVOLVING HYDROGEN ATOMS REMARK 500 1.6 ANGSTROMS FOR CONTACTS INVOLVING HYDROGEN ATOMS REMARK 500 REMARK 500 ATM1 RES C SSEQI ATM2 RES C SSEQI SSYMOP DISTANCE REMARK 500 O HOH A 143 O HOH A 143 2656 1.51 REMARK 500 REMARK 500 REMARK: NULL REMARK 500 REMARK 500 GEOMETRY AND STEREOCHEMISTRY REMARK 500 SUBTOPIC: TORSION ANGLES REMARK 500 REMARK 500 TORSION ANGLES OUTSIDE THE EXPECTED RAMACHANDRAN REGIONS: REMARK 500 (M=MODEL NUMBER; RES=RESIDUE NAME; C=CHAIN IDENTIFIER; REMARK 500 SSEQ=SEQUENCE NUMBER; I=INSERTION CODE). REMARK 500 REMARK 500 STANDARD TABLE: REMARK 500 FORMAT:(10X,I3,1X,A3,1X,A1,I4,A1,4X,F7.2,3X,F7.2) REMARK 500 REMARK 500 EXPECTED VALUES: GJ KLEYWEGT AND TA JONES (1996). PHI/PSI- REMARK 500 CHOLOGY: RAMACHANDRAN REVISITED. STRUCTURE 4, 1395 - 1400 REMARK 500 REMARK 500 M RES CSSEQI PSI PHI REMARK 500 GLU A 2 -123.35 68.45 REMARK 500 REMARK 500 REMARK: NULL REMARK 900 REMARK 900 RELATED ENTRIES REMARK 900 RELATED ID: TTK003001768.1 RELATED DB: TARGETDB DBREF 1WK2 A 1 121 UNP Q5SM30 Q5SM30_THET8 1 121 SEQRES 1 A 121 MSE GLU ARG PRO LYS LEU GLY LEU ILE VAL ARG GLU PRO SEQRES 2 A 121 TYR ALA SER LEU ILE VAL ASP GLY ARG LYS VAL TRP GLU SEQRES 3 A 121 ILE ARG ARG ARG LYS THR ARG HIS ARG GLY PRO LEU GLY SEQRES 4 A 121 ILE VAL SER GLY GLY ARG LEU ILE GLY GLN ALA ASP LEU SEQRES 5 A 121 VAL GLY VAL GLU GLY PRO PHE SER VAL GLU GLU LEU LEU SEQRES 6 A 121 ALA HIS GLN GLU LYS HIS LEU ALA GLU GLU ALA PHE LEU SEQRES 7 A 121 ARG ALA TYR ALA LYS ASP GLU PRO LEU TYR ALA TRP VAL SEQRES 8 A 121 LEU GLU ASN ALA PHE ARG TYR GLU LYS PRO LEU HIS VAL SEQRES 9 A 121 PRO ARG ARG PRO GLY ARG VAL MSE PHE VAL ASP LEU SER SEQRES 10 A 121 GLU VAL ARG TRP MODRES 1WK2 MSE A 1 MET SELENOMETHIONINE MODRES 1WK2 MSE A 112 MET SELENOMETHIONINE HET MSE A 1 8 HET MSE A 112 8 HETNAM MSE SELENOMETHIONINE FORMUL 1 MSE 2(C5 H11 N O2 SE) FORMUL 2 HOH *45(H2 O) HELIX 1 1 PRO A 13 ASP A 20 1 8 SHEET 1 A 5 GLY A 7 ILE A 9 0 SHEET 2 A 5 GLY A 36 SER A 42 1 O GLY A 39 N LEU A 8 SHEET 3 A 5 ARG A 45 GLY A 54 -1 O LEU A 52 N GLY A 36 SHEET 4 A 5 TYR A 88 HIS A 103 -1 O LEU A 102 N LEU A 46 SHEET 5 A 5 TRP A 25 ARG A 28 -1 N ARG A 28 O TYR A 88 LINK C MSE A 1 N GLU A 2 1555 1555 1.33 LINK C MSE A 112 N PHE A 113 1555 1555 1.32 CISPEP 1 GLU A 12 PRO A 13 0 0.21 CISPEP 2 VAL A 104 PRO A 105 0 -0.02 CRYST1 52.583 55.846 43.186 90.00 96.60 90.00 C 1 2 1 4 ORIGX1 1.000000 0.000000 0.000000 0.00000 ORIGX2 0.000000 1.000000 0.000000 0.00000 ORIGX3 0.000000 0.000000 1.000000 0.00000 SCALE1 0.019018 0.000000 0.002200 0.00000 SCALE2 0.000000 0.017906 0.000000 0.00000 SCALE3 0.000000 0.000000 0.023310 0.00000 HETATM 1 N MSE A 1 18.982 47.249 -0.899 1.00 26.17 N HETATM 2 CA MSE A 1 17.499 47.225 -0.778 1.00 26.17 C HETATM 3 C MSE A 1 16.990 46.793 -2.147 1.00 26.17 C HETATM 4 O MSE A 1 17.782 46.507 -3.046 1.00 26.17 O HETATM 5 CB MSE A 1 16.965 48.615 -0.393 1.00 26.17 C HETATM 6 CG MSE A 1 15.597 48.645 0.327 1.00 26.17 C HETATM 7 SE MSE A 1 15.179 50.382 1.193 1.00 26.17 SE HETATM 8 CE MSE A 1 15.290 49.864 3.050 1.00 26.17 C