Structure activity relationships of glycosyl transferases involved in protein O mannosylation in the actinobacteria

Actinobacteria have a protein O-glycosylation system that resembles eukaryotic protein Omannosylation. Both M. tuberculosis and S. coelicolor have growth retarded phenotypes when a membrane bound protein O-mannosyl transferase (Pmt), which transfers mannose from polyprenol phosphate mannose to a target protein, is absent. Moreover, S. coelicolor pmt - mutants are resistant to infection by ϕC31 phage and have increased susceptibility to vancomycin and several β-lactams. S. coelicolor strains that lack polyprenol phosphate mannose synthase (Ppm1), which transfers mannose from GDP-mannose to polyprenol phosphate, are even more susceptible to antibiotics and a ppm1 - mutant in M. tuberculosis is lethal. Pmt and Ppm1 are therefore possible new targets for the isolation of novel antimicrobials to be used against M. tuberculosis. The aim of this PhD thesis was to gain a deeper understanding of the structure and function of both S. coelicolor enzymes. For Ppm1, ten mutant alleles (the majority being individual alanine substitutions) were tested and eight were essential for S. coelicolor DT3017, a ppm1 - strain, complementation, with four of the corresponding residues positioned close to the predicted catalytic DXD ... (continues)