The long term objective of this investigation is directed towards understanding more fully the biochemical and physiological importance and function of two cell surface components, the poly(gamma-D-glutamyl) capsule of Bacillus licheniformis and polymers containing polysialic acid residues in Escherichia coli. A second major objective is to understand more fully the conformation, molecular motions and interactions of glycosyl carrier polyisoprenoids in membranes. Effort during the least several years has been concerned with the structure and biosynthesis of these two surface polymers. On the basis of work already accomplished (determination of the structure of the poly(gamma-D-glutamyl) capsule; biosynthetic studies on the meembranous polyglutamyl synthetase and sialyltransferase complex; isolation, characterization and role of undecaprenyl phosphate in sialyl polymer synthesis; direction of polymer elongation; role of a temperature-induced alteration in sialyl polymer assembly) these objectives are a logical continuation of studies currently in progress which include elucidation of the molecular events whereby membranous enzyme interactions participate in the synthesis and assembly of these surface components and the interaction of several paramagnetic isoprenoid carrier lipids with phospholipid membranes. In sialyl polymer synthesis, major emphasis will continue to focus upon: 1) the mechanism of assembly of the sialyltransferase complex; 2) structural studies on the nature of in vitro and in vivo synthesized polymers; 3) the interaction of spin-labeled polyisoprenyl phosphate derivatives with phospholipid membranes and reconstituted membrane vesicles. Future studies on the biosynthesis of the poly(gamma-D-glutamyl) polymers will be directed at understanding the mechanism of activation, racemization and polymerization of this unique polymer. The nature of a putative thioester intermediate will be pursued.
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