Sequestration of origins of chromosome replication in Escherichia coli by lipid compartments: the pocket hypothesis.
After initiation of chromosome replication in Escherichia coli, the newly replicated, hemi-methylated origins of replication are exempt from both re-initiation and methylation for up to a third of the generation time. In the model proposed here, the exemption from methylation is attributed to the phospholipid preferences of proteins binding hemi-methylated origins to membrane; these proteins associate with unsaturated phosphatidylethanolamine which forms structures with small radii of curvature; hence, a lipid compartment or "pocket" forms around the origin making it inaccessible to cytoplasmic enzymes such as Dam methyltransferase. Since autolysins and peptidoglycan-synthesizing enzymes are sensitive to lipid composition, peptidoglycan synthesis is stimulated around this compartment and creates structures obtained in membrane fractionation that specifically bind hemi-methylated origins.
Norris
V
V
Department of Microbiology, School of Medicine, University of Leicester, U.K.
D001426:Bacterial Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology; D002876:Chromosomes, Bacterial / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D050356:Lipid Metabolism; D008745:Methylation; D008954:Models, Biological; D010714:Phosphatidylethanolamines / Q000378:metabolism
D001426:Bacterial Proteins; D010714:Phosphatidylethanolamines