Biochemical Studies of Bacterial Protein Export
Studies on the mechanisms of protein secretion and transport have been, until recently, confined to animal cells. In the past few years genetic and biochemical studies with bacteria have contributed greatly to our knowledge of mechanisms of protein secretion and localization (reviews by Davis and Tai 1980; Wickner 1980; Osborn and Wu 1980; Michaelis and Beckwith 1982; Randall and Hardy 1984; Benson et al. 1985). In particular, selection of mutants has permitted the definition of the function of the cleavable signal sequence and the identification of many gene products that may be involved in protein export (see Beckwith and Ferro-Novick, this volume; Lunn et al., this volume). In addition, several signal peptidases have been purified and characterized and their genes identified (Date and Wickner 1981; Innis et al. 1984; Yu et al. 1984; Zwizinski and Wickner 1980; Ray et al., this volume). Moreoever, since the outer surface of the bacterial membrane is readily accessible to manipulation, we have been able to use extracellular radioactive labeling or protease digestions of protruding secreted nascent chains to demonstrate directly the contranslational secretion (Smith et al. 1977, 1978) that had been inferred from the earlier in vitro work. The study of accessibility of nascent chains accumulates on the inner surface of the cytoplasmic membrane before the chains reach the outer surface (Randall 1983).
KeywordsMembrane Vesicle Protein Translocation Signal Peptidase Protein Export Nascent Chain
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