The function of galactosyl phosphorylpolyprenol in biosynthesis of lipoteichoic acid in Bacillus coagulans.

Incubation of UDP-[14C]galactose with membranes of Bacillus coagulans led to the formation of a radioactive glycolipid, which was tentatively characterized as beta-galactosyl phosphorylpolyprenol (Gal-P-prenol) on the basis of its chromatographic behavior and data from structural analysis of its sugar 1-phosphate moiety. The sugar moiety of [14C]Gal-P-prenol was shown to be incorporated into a membrane-bound polymer, which coincided with the diacyl form of lipoteichoic acid in its chromatographic behavior on columns of Sephacryl S-300, DEAE-Sephacel and octyl-Sepharose. Hydrogen fluoride hydrolysis of the polymer afforded an alpha-galactoside identical with Gal(alpha 1----2)Gro obtained from lipoteichoic acids. The incorporation of galactose residues from [14C]Gal-P-prenol into the polymer was greatly enhanced by exogenous lipoteichoic acids, especially of the diacyl and monoacyl forms. The optimal pH and metal concentration for the Gal-P-prenol formation, respectively, were found to be 8.4 and 10 mM (MgCl2), whereas those for the transfer of galactose from this lipid intermediate to polymer were 4.5 and 16 mM (CaCl2). The above results lead to the conclusion that Gal-P-prenol serves as the direct galactosyl donor in the synthesis of lipoteichoic acids in B. coagulans.