Localization of the binding site for the oligosaccharide moiety of Gb(3) on verotoxin 1 using NMR residual dipolar coupling measurements

By use of NMR residual dipolar coupling measurements in a dilute liquid-cry stalline solvent, the solution structure has been determined of the complex between the oligosaccharide moiety of globotriaosylceramide (Gb(3)-OS) and the B-subunit homopentamer of verotoxin 1 (VTB). The dipolar coupling data indicate that Gb(3)-OS binds in a single binding site per monomer, which i s identical to one of three sites inferred from the X-ray structure of the same complex. We find no evidence within experimental error for occupancy a t either of the two additional binding sites observed per monomer in the cr ystal structure.