title: Structure-function analysis of Arg-Gly-Asp helix motifs in alpha v beta 6 integrin ligands.
abstract: Data relating to the structural basis of ligand recognition by integrins are limited. Here we describe the physical requirements for high affinity binding of ligands to alpha v beta6. By combining a series of structural analyses with functional testing, we show that 20-mer peptide ligands, derived from high affinity ligands of alpha v beta6 (foot-and-mouth-disease virus, latency associated peptide), have a common structure comprising an Arg-Gly-Asp motif at the tip of a hairpin turn followed immediately by a C-terminal helix. This arrangement allows two conserved Leu/Ile residues at Asp(+1) and Asp(+4) to be presented on the outside face of the helix enabling a potential hydrophobic interaction with the alpha v beta6 integrin, in addition to the Arg-Gly-Asp interaction. The extent of the helix determines peptide affinity for alpha v beta6 and potency as an alpha v beta6 antagonist. A major role of this C-terminal helix is likely to be the correct positioning of the Asp(+1) and Asp(+4) residues. These data suggest an explanation for several biological functions of alpha v beta6 and provide a structural platform for design of alpha v beta6 antagonists.
authors.affiliation: Tumour Biology Centre, Cancer Research UK Clinical Centre, Queen Mary's College, Barts, Charterhouse Square, London EC1M 6BQ, United Kingdom; London Medical and Dental School, John Vane Science Centre, Charterhouse Square, London EC1M 6BQ, United Kingdom.
authors.forename: Danielle
authors.initials: D
authors.lastname: DiCara
authors.affiliation: Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom.
authors.forename: Chiara
authors.initials: C
authors.lastname: Rapisarda
authors.affiliation: Department of Biomedical Engineering, University of California, Davis, California 95616-5294.
authors.forename: Julie L
authors.initials: JL
authors.lastname: Sutcliffe
authors.affiliation: Biogen Idec Inc., Cambridge Center, Cambridge, Massachusetts 02142.
authors.forename: Shelia M
authors.initials: SM
authors.lastname: Violette
authors.affiliation: Biogen Idec Inc., Cambridge Center, Cambridge, Massachusetts 02142.
authors.forename: Paul H
authors.initials: PH
authors.lastname: Weinreb
authors.affiliation: Tumour Biology Centre, Cancer Research UK Clinical Centre, Queen Mary's College, Barts, Charterhouse Square, London EC1M 6BQ, United Kingdom; London Medical and Dental School, John Vane Science Centre, Charterhouse Square, London EC1M 6BQ, United Kingdom.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Hart
authors.affiliation: Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom. Electronic address: m.j.howard@kent.ac.uk.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Howard
authors.affiliation: Tumour Biology Centre, Cancer Research UK Clinical Centre, Queen Mary's College, Barts, Charterhouse Square, London EC1M 6BQ, United Kingdom; London Medical and Dental School, John Vane Science Centre, Charterhouse Square, London EC1M 6BQ, United Kingdom. Electronic address: john.marshall@cancer.org.uk.
authors.forename: John F
authors.initials: JF
authors.lastname: Marshall
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm / Q000737:chemistry / Q000378:metabolism*; D016466:CHO Cells; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D016023:Integrins / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
chemical_list: D000951:Antigens, Neoplasm; D016023:Integrins; D008024:Ligands; D009842:Oligopeptides; D010446:Peptide Fragments; C073878:integrin alphavbeta6; C047981:arginyl-glycyl-aspartic acid