Synthesis and Assembly of the Outer Membrane Proteins OmpA and OmpF of Escherichia coli

This chapter focuses on the synthesis and assembly of the outer memberane proteins OmpA and OmpF of Escherichia coli. These proteins are present in high concentrations. Early studies suggest that these proteins might be synthesized unusually slowly, yet without the appearance of transient intermediates either in the form of precursor molecules or as a pool of newly synthesized molecules in the inner membrane. However, mature lipoprotein has been detected in the inner membrane. Recent work has shown that both OmpA and OmpF are synthesized at the same rate as other cell proteins and as precursor molecules that associate first with the inner membrane and are subsequently processed rapidly to mature protein. The kinetics of processing suggests that there may be as many as three processing pathways, the relative contribution of which may be temperature dependent. Quantitative analysis requires the use of a double-labeling methodology and knowledge of the primary sequence of the protein(s) under investigation.