Solution conformation of various uridine diphosphoglucose salts as probed by NMR spectroscopy

The solution conformations of uridine diphosphoglucose (UDP-Glc) under a va riety of conditions (solvent, ionic strength, various mono- and divalent ca tions) have been studied by NMR spectroscopy (H-1, C-13, P-31, and Mg-25). In the case of divalent cations (Ca2+, Mg2+, Mn2+) the phosphate oxygens ar e the preferred coordination sites and analysis of the Mg-25 linewidths of solutions with various [Mg2+]/[UDP-Glc] ratios, indicates that the 1:1 Mg2-UDP-Glc complex is the major species. From C-13 relaxation data and hydrod ynamic theory, it has been demonstrated that under all conditions UDP-Glc a dopts a fairly extended overall shape and that magnesium ions lead to a sig nificant increase in the average length of the UDP-Glc molecule as compared to monovalent cations. Thus, one of the roles of the metal ion in enzymic reactions involving nucleotide sugars may be to preorganize the nucleotide sugar. (C) 2000 Elsevier Science Ltd. All rights reserved.