Biogenesis and functions of model integral outer membrane proteins:TI Biogenesis and functions of model integral outer membrane proteins: Escherichia coli OmpA and Pseudomonas aeruginosa OprF

摘要

Gram-negative bacteria, such as Escherichia coli and Pseudomonas aeruginosa, are surrounded by two concentric membranes that differ in structure, composition and function. Whereas both lea?ets of the inner membrane are composed of phospholipids, the outer membrane is asymmetric – the inner lea?et is composed of phospholipids and the outer lea?et of lipopolysaccharides. The inner membrane is the major permeability barrier between the external environment and the cytoplasm and it carries out energy-driven functions, whereas the outer membrane serves as a passive molecular sieve, allowing the import and export of requisite substances while preventing the entry of harmful ones. The two membranes are separated by an aqueous periplasm that contains soluble proteins and the peptidoglycan layer, a major component of the cell wall.