Final steps of the maturation of Omp F, a major protein from the outer membrane of Escherichia coli

Abstract

Pulse-labelling experiments with E. coli cells allowed us to follow the incorporation of de novo proteins into the outer membrane of the cell envelope. Labelled membrane samples containing increasingly different levels of newly synthesized Omp F protein were subjected to chemical cross-linking with a bifunctional cleavable reagent in order to investigate the process of trimer formation of the protein. From the results obtained, we conclude that the formation of functional Omp F trimers is substantially delayed to, and can be distinguished from, the incorporation of Omp F monomers to the outer membrane. E. coli Outer membrane Porin protein Omp F Membrane biogenesis Chemical cross-linking

The complete general secretory pathway in gram-negative bacteria.

“…Furthermore, simple tests such as solubility in the detergent Sarkosyl, as used by some authors (see, e.g., reference 56), may not indicate the true location of assembly intermediates in the cells. OmpF monomers were found associated with outer membrane-derived vesicles in one study (25), and OmpF monomers secreted by spheroplasts remain monomeric until they are mixed with cell envelopes (499). Both of these studies suggest that trimerization occurs at the surface of or within the outer membrane, possibly via partially folded monomeric and dimeric forms (111,112,460).…”

“…24). The 25. Alignment of the amino acids (single-letter code) in the amino-terminal segments of type IV prepilins with those of the corresponding segments of four Pul proteins that form part of the main terminal branch of the GSP in K oxytoca and with ComG.3, one of the prepilin-like proteins required for transformation competence in B. subtilis.…”