Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 218

The targeting factors recognize proteins to be transported into or through the inner membrane and help target them to the membrane. Which type of signal sequence a protein has determines which of the targeting factors directs it to the SecYEG translocon. Enteric bacteria like E. coli have at least two separate systems that target proteins to and through the membranes. The SecB system is dedicated to proteins that are directed through the inner membrane into the periplasm or exported from the cell. The signal recognition particle (SRP) system seems to be dedicated to proteins that are mostly destined to reside in the inner membrane. Another protein, SecA, participates in both pathways, at least for some proteins; it is found in all bacteria, but not in archaea or eukaryotes, although in eukaryotes other proteins may play a similar role.