FTSY, THE PROKARYOTIC SIGNAL RECOGNITION PARTICLE RECEPTOR HOMOLOG, IS ESSENTIAL FOR BIOGENESIS OF MEMBRANE-PROTEINS

In mammalian cells, many secretory proteins are targeted to the endopl asmic reticulum co-translationally, by the signal recognition particle (SRP) and its receptor. In Escherichia coli, the targeting of secreto ry proteins to the inner membrane can be accomplished post-translation ally. Unexpectedly, despite this variance, E. coli contains essential genes encoding Ffh and FtsY with a significant similarity to proteins of the eukaryotic SRP machinery. In this study, we investigated the po ssibility that the prokaryotic SRP-like machinery is involved in bioge nesis of membrane proteins in E. coli. The data presented here demonst rate that the SRP-receptor homologue, FtsY, is indeed essential for ex pression of integral membrane proteins in E. coli, indicating that, in the case of this group of proteins, FtsY and the mammalian SRP recept or have similar functions.