tRNA-abhängige Biosynthesis of Phospholipids in Pseudomonas aeruginosa

点击翻译按钮获取中文摘要

Bacterial membranes undergo permanent changes in their composition in response to varying environmental conditions to efficiently fulfil their biological tasks. For this purpose lipids are covalently modified for instance by adding lysine onto phosphatidylglycerol (PG), thereby altering the net negative charge of the membrane. This lipid modification mediates resistance to cationic antimicrobial peptides (CAMPs) in Gram positive bacteria. Recently we discovered the tRNA-dependent addition of alanine to PG with the formation of a new phospholipid alanyl-phosphatidylglycerol (A-PG) in the Gram negative pathogen Pseudomonas aeruginosa mediating resistance against two positively charged antibacterial agents, a β-lactam antibiotic, high concentrations of H+ and lactate. Here we want to elucidate the tRNA-dependent enzyme mechanism and the mode of substrate recognition for the corresponding alanyl-phosphatidylglycerol synthase (A-PGS) using purified recombinant P. aeruginosa enzyme and advanced biochemical and biophysical techniques. A crystal structure will provide the understanding of the involved structure-function relationships. Novel biochemical principles of general importance are expected. Furthermore the physiological and biophysical role of A-PG formation versus L-PG formation will be elucidated. Finally the influence of alkaline conditions on the lipid composition will be analyzed analogously.