EARLY EVENTS IN PREPROTEIN RECOGNITION IN ESCHERICHIA-COLI - INTERACTION OF SRP AND TRIGGER FACTOR WITH NASCENT POLYPEPTIDES

In Escherichia coil, components of a signal recognition particle (SRP) and its receptor have been identified which appear to be essential fo r efficient translocation of several proteins, In this study we use cr oss-linking to demonstate that E. coli SRP interacts with a variety of nascent presecretory proteins and integral inner membrane proteins, E vidence is presented that the interaction is correlated with the hydro phobicity of the core region of the signal sequence and thereby with i ts ability to promote transport in vivo, A second E. coli component, w hich is identified as trigger factor, can be efficiently cross-linked to all tested nascent chains derived from both secreted and cytosolic proteins, We propose that SRP and trigger factor act as secretion-spec ific and general molecular chaperone respectively, early in protein sy nthesis.