REFINED STRUCTURE AND DISULFIDE PAIRING OF THE KALATA B1 PEPTIDE
Refined structure and metal binding site of the kalata B1 peptide.
Elucidation of the Primary and Three-Dimensional Structure of the Uterotonic Polypeptide Kalata B1
Extracted from African plant kalata-kalata
STRUCTURE WAS DETERMINED USING NOES FROM A SINGLE 100 MS MIXING TIME NOESY EXPERIMENT
STRUCTURES ARE BASED ON A TOTAL OF 333 DISTANCE CONSTRAINTS. THIS INCLUDES 6 UPPER AND 6 LOWER LIMITS DEFINING 3 DISULFIDE BONDS, AS WELL AS 3 UPPER AND 3 LOWER LIMITS DEFINING A PEPTIDE BOND CYCLIZING THE PEPTIDE BACKBONE. RESIDUE NUMBERING FOLLOWS THE ORIGINAL DESCRIPTION OF CITATION 1, EXCEPT THAT FOR THE PURPOSES OF STRUCTURE CALCULATIONS, THE N-TERMINAL RESIDUE WAS TAKEN AS ASN8. THEREFORE, RESIDUES 30-36 IN THIS DEPOSITION CORRESPOND TO RESIDUES 1-7 IN CITATION 1 AND RELATED PDB ENTRY 1KAL. STRUCTURES WERE REFINED IN THE ABSENCE OF ANY ARTIFICIAL CONSTRAINTS DEFINING DISULFIDE BONDS UNTIL ALL NOES HAD BEEN ASSIGNED AND LOW TARGET FUNCTIONS WERE ACHIEVED (TF=0.6). 15 ADDITIONAL CALCULATIONS WERE PERFORMED WITH THESE INPUT DATA AND THE INCLUSION OF CONSTRAINTS DEFINING ALL POSSIBLE DISULFIDE PAIRING COMBINATIONS. THE STRUCTURES CONTAINING DISULFIDES BETWEEN [5(34)-13], [17-29] AND [22-27] DISPLAYED THE LOWEST TARGET FUNCTION (0.74, SECOND LOWEST WAS 1.54). ON THE BASIS OF THIS RESULT AND ANALYSIS OF NOES OBSERVED BETWEEN CYS SIDECHAIN PROTONS, THIS DISULFIDE BONDING ARRANGEMENT WAS ASSUMED TO BE CORRECT AND SERVED AS THE BASIS FOR THIS DEPOSITION.
CYCLIC PEPTIDE, CYCLOTIDE, DISULFIDE PAIRING, UTEROTONIC, PLANT PROTEIN