title: Solution structure of a cyclic RGD peptide that inhibits platelet aggregation.
abstract: Peptides containing the Arg-Gly-Asp (RGD) sequence can inhibit platelet aggregation. Incorporation of this sequence into a cyclic peptide results in specific binding to a particular integrin. Studies of cyclic RGD peptides show that residues surrounding the RGD sequence have important effects on the selectivity of the peptide to bind with glycoprotein IIb/IIIa (GPIIb/IIIa). In this paper, we elucidate the conformation of cyclo(2,10)Ac-Gly1-Pen2-Gly3-His4-Arg5-Gly6-Asp7 -Leu8-Arg9-Cys10-Ala11-NH2 (1) by NMR and molecular dynamics simulations. This peptide inhibits platelet aggregation in a manner similar to that reported for cyclo(2,10)Gly1-Pen2-Gly3-His4-Arg5-Gly6-Asp7-Le u8-Arg9-Cys10-Ala11-OH (6) (Cheng, S. et al. J. Med. Chem. 1994, 37, 1-8), which is shown to be selective for the GPIIb/IIIa receptor. The cyclic peptide 1 exhibited a major and a minor conformer in solution. In the major conformer, the His4-Arg5-Gly6-Asp7 segment encompasses a 4-->1 hydrogen bond with a distorted type II beta-turn, and the minor conformer has turn-extended-turn. A comparison between the major conformation of this peptide and those of other cyclic RGD peptides suggests the importance of a hydrophobic residue adjacent to the RGD sequence.
authors.affiliation: Department of Pharmaceutical Chemistry, University of Kansas, Lawrence 66047, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Jois
authors.forename: U S
authors.initials: US
authors.lastname: Tambunan
authors.forename: S
authors.initials: S
authors.lastname: Chakrabarti
authors.forename: T J
authors.initials: TJ
authors.lastname: Siahaan
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects*; D011487:Protein Conformation; D011522:Protons; D012996:Solutions; D013329:Structure-Activity Relationship
chemical_list: D009842:Oligopeptides; D010456:Peptides, Cyclic; D011522:Protons; D012996:Solutions; C047981:arginyl-glycyl-aspartic acid