THE ESCHERICHIA-COLI SRP - PREFERENCES OF A TARGETING FACTOR

Research on the targeting of proteins to the cytoplasmic membrane of E . coli has mainly focused on the so-called 'general secretory pathway' (GSP) which involves the Sec-proteins. Recently, evidence has been ob tained for an alternative targeting pathway in E. coli which involves the signal recognition particle (SRP). The constituents of this SRP pa thway in E. coli are homologous to those of the well-characterized euk aryotic SRP pathway, which is the main targeting pathway for both prot eins translocated across and inserted into the endoplasmic reticulum m embrane. However, until recently, no clear function could be assigned to the SRP in E. coli. New studies point to an important role of the E . coli SRP in the assembly of inner membrane proteins. (C) 1997 Federa tion of European Biochemical Societies.