SOLUTION CONFORMATION OF ALPHA-METHYLGLUTAMYL-CONTAINING, BETA-METHYLGLUTAMYL-CONTAINING OR GAMMA-METHYLGLUTAMYL-CONTAINING DERIVATIVES AS PROBES OF VITAMIN-K-DEPENDENT CARBOXYLASE USING MOLECULAR MODELING ANDNUCLEAR-MAGNETIC-RESONANCE

in the present study, the conformational behaviour of methyl substitut ed N-BOC glutamic acid methyl esters (2M, 3T, 3E, 4T, 4E) has been com pletely characterized through combined NMR and molecular modeling stud ies. Hetero- and homonuclear coupling constants were measured in order to assign the remaining diastereotopic methylene protons at C(3) and/ or C(4), and used for comparison with theoretical data. In parallel, t he complete conformational analysis of these analogues has been achiev ed using molecular mechanics and molecular dynamics (MD)methods. The c onformation of the glutamyl residue is established by the excellent ag reement between the experimental and calculated side chain scalar coup ling constants. The theoretical NMR data were calculated taking into a ccount all the accessible conformations and using the averaging method s appropriate for internal motions. There is a significant influence o f the methyl group on the conformational behaviour and on the biologic al relevance of these structures. Steric effect or electrostatic inter action may also have a considerable influence in stabilizing a conform ational population in D2O solution. The conformational preferences of those different analogues in aqueous and methanol solution are discuss ed in the light of biological results obtained on the vitamin K-depend ent carboxylase system. (C) 1997 Elsevier Science B.V.