Conformation of beta-methylmelibiose bound to the ricin B-chain as determined from transferred nuclear Overhauser effects.
Transferred nuclear Overhauser effect (TRNOE) experiments have revealed a change in the torsion angles about the alpha-1-6 glycosidic bond of methyl beta-melibioside upon binding of the melibioside to the ricin B-chain (Rb). A full relaxation rate matrix simulation of experimental buildup curves aided in quantitative interpretation of 1D selective inversion recovery TRNOE experiments. The data are consistent with a model in which both major (omega approximately 170 degrees) and minor (omega approximately -60 degrees) conformers for methyl beta-melibioside are significantly populated in solution while the Rb/methyl beta-melibioside complex has little of the minor conformer populated. The results indicate that the ricin B-chain excludes binding of certain ligand conformations on the basis of unfavorable interactions between the protein surface and remote portions of the disaccharide system.
Bevilacqua
V L
VL
Department of Chemistry, Yale University, New Haven, Connecticut 06511.
Kim
Y
Y
Prestegard
J H
JH
D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008553:Melibiose / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D037121:Plant Lectins; D010947:Plants, Toxic; D012276:Ricin / Q000737:chemistry*; D012278:Ricinus / Q000737:chemistry
D008024:Ligands; D037121:Plant Lectins; C077178:beta-methylmelibiose; D012276:Ricin; D008553:Melibiose