1H n.m.r. studies of the structure of ristocetin A and of its complexes with bacterial cell wall analogues in aqueous solution

Abstract

The conformation of ristocetin A in aqueous solution is shown to be very similar to that previously found in dimethyl sulphoxide solution. In particular, there is a cleft on one face which binds the carboxylate anion of bacterial cell wall analogues, and which is not fully accessible to the solvent. Binding studies with the analogues N-acetyl-D-alanyl-D-alanine and N,N-diacetyl-L-lysyl-D-alanyl-D-alanine indicate that the structures of the complexes with ristocetin A are also very similar to those previously found in dimethyl sulphoxide solution; again, there is very unusual behaviour of some amide protons. Two-dimensional nuclear Overhauser effect studies in D₂O show that the Iysyl side chain is in a different orientation in aqueous solution to that found in dimethyl sulphoxide.