title: Concerted motions of the integrin-binding loop and the C-terminal tail of the non-RGD disintegrin obtustatin.
abstract: Obtustatin is a potent and selective inhibitor of the alpha1beta1 integrin in vitro and of angiogenesis in vivo. It possesses an integrin recognition loop that harbors, in a lateral position, the inhibitory 21KTS23 motif. We report an analysis of the dynamics of the backbone and side-chain atoms of obtustatin by homonuclear NMR methods. Angular mobility has been calculated for 90 assigned cross-peaks from 22 off-resonance rotating frame nuclear Overhauser effect spectroscopy spectra recorded at three magnetic fields. Our results suggest that the integrin binding loop and the C-terminal tail display concerted motions, which can be interpreted by hinge effects. Among the integrin-binding motif, threonine 22 and serine 23 exhibit the lowest and the highest side-chain flexibility, respectively. It is noteworthy that the side chain of threonine 22 is not solvent-exposed, although based on synthetic peptides it appears to be the most critical residue for the inhibitory activity of obtustatin on the binding of integrin alpha1beta1 to collagen IV. Instead, the side chain of threonine 22 is oriented toward the loop center and hydrogen-bonded to residues Thr25 and Ser26. This network of interactions explains the restrained mobility of threonine 22 and suggests that its functional importance lies in maintaining the active conformation of the alpha1beta1 inhibitory loop.
authors.affiliation: Departamento de Química Física and Servicio Central de Soporte a la Investigación Experimental, Universitat de Valencia, Dr. Moliner 50, 46100 Burjassot (Valencia), Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Monleon
authors.forename: M Paz
authors.initials: MP
authors.lastname: Moreno-Murciano
authors.forename: Helena
authors.initials: H
authors.lastname: Kovacs
authors.forename: Cezary
authors.initials: C
authors.lastname: Marcinkiewicz
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Calvete
authors.forename: Bernardo
authors.initials: B
authors.lastname: Celda
mesh_terms: D000409:Alanine / Q000737:chemistry; D020816:Amino Acid Motifs; D003094:Collagen / Q000737:chemistry; D006860:Hydrogen Bonding; D039222:Integrin alpha1beta1 / Q000378:metabolism; D016023:Integrins / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015233:Models, Statistical; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012694:Serine / Q000737:chemistry; D013912:Threonine / Q000737:chemistry; D014757:Viper Venoms / Q000737:chemistry*
chemical_list: D039222:Integrin alpha1beta1; D016023:Integrins; D010455:Peptides; D014757:Viper Venoms; C474313:obtustatin, Vipera lebetina obtusa; D013912:Threonine; D012694:Serine; D003094:Collagen; D000409:Alanine