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THE CYCLIC PEPTIDE CONTRYPHAN-R FROM CONUS RADIATUS
Structural highlights
FunctionCOW_CONRA Its target is unknown, but this toxin may modulate voltage-activated calcium channels (Cav) or calcium-dependent potassium channels (KCa).[UniProtKB:P0C248][UniProtKB:P0C250][UniProtKB:P62903][UniProtKB:P83047] Publication Abstract from PubMedContryphan-R is a disulfide-constrained octapeptide containing a D-tryptophan that was isolated recently from venom of the cone shell Conus radiatus. The polypeptide is present in two forms in solution due to cis-trans isomerization at hydroxyproline 3. The solution structure of the major form of this unusual polypeptide, determined from NMR data, consists of a well-defined fold containing a non-hydrogen-bonded chain reversal from Gly1 to Glu5, which includes a cis-hydroxyproline and a D-Trp, and a type I beta-turn from Glu5 to Cys8. The presence of a putative salt bridge between the Glu5 carboxyl group and the N-terminal ammonium group is investigated by using various solvation models during energy minimization and is compared with the results of a pH titration. A comparison of the structure of contryphan-R with other cyclic peptide structures highlights some of the key structural determinants of these peptides and suggests that the contryphan-R fold could be exploited as a scaffold onto which unrelated protein binding surfaces could be grafted. Comparison with small disulfide-bridged loops in larger proteins shows that contryphan-R is similar to a commonly occurring loop structure found in proteins. Solution structure of contryphan-R, a naturally occurring disulfide-bridged octapeptide containing D-tryptophan: comparison with protein loops.,Pallaghy PK, Melnikova AP, Jimenez EC, Olivera BM, Norton RS Biochemistry. 1999 Aug 31;38(35):11553-9. PMID:10471307[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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