NMR-STUDIES OF THE CONFORMATION OF THIOCELLOBIOSE BOUND TO A BETA-GLUCOSIDASE FROM STREPTOMYCES SP

The conformation of 4-thiocellobiose bound to beta-glucosidase from St reptomyces sp. has been studied by H-1-NMR transferred nuclear Overhau ser effect spectroscopy (TR-NOE), Thiocellobiose behaves as an inhibit or of this glucosidase when cellobiose is used as substrate. NOE measu rements and molecular mechanics calculations have also been performed to estimate the probability distribution of conformers of thiocellobio se when free in solution. Experimental data show that, in contrast wit h the natural O-analogue, thiocellobiose presents three conformational families in the free state, namely syn, anti-Psi and anti-Phi, whilst only one of them (syn) is recognized by the enzyme. (C) 1998 Federati on of European Biochemical Societies.