title: Nascent membrane and presecretory proteins synthesized in Escherichia coli associate with signal recognition particle and trigger factor.
abstract: The Escherichia coli signal recognition particle (SRP) and trigger factor are cytoplasmic factors that interact with short nascent polypeptides of presecretory and membrane proteins produced in a heterologous in vitro translation system. In this study, we use an E. coli in vitro translation system in combination with bifunctional cross-linking reagents to investigate these interactions in more detail in a homologous environment. Using this approach, the direct interaction of SRP with nascent polypeptides that expose particularly hydrophobic targeting signals is demonstrated, suggesting that inner membrane proteins are the primary physiological substrate of the E. coli SRP. Evidence is presented that the overproduction of proteins that expose hydrophobic polypeptide stretches, titrates SRP. In addition, trigger factor is efficiently cross-linked to nascent polypeptides of different length and nature, some as short as 57 amino acid residues, indicating that it is positioned near the nascent chain exit site on the E. coli ribosome.
authors.affiliation: Department of Microbiology, Institute of Molecular Biological Sciences, Biocentrum Amsterdam, The Netherlands.
authors.forename: Q A
authors.initials: QA
authors.lastname: Valent
authors.forename: J W
authors.initials: JW
authors.lastname: de Gier
authors.forename: G
authors.initials: G
authors.lastname: von Heijne
authors.forename: D A
authors.initials: DA
authors.lastname: Kendall
authors.forename: C M
authors.initials: CM
authors.lastname: ten Hagen-Jongman
authors.forename: B
authors.initials: B
authors.lastname: Oudega
authors.forename: J
authors.initials: J
authors.lastname: Luirink
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D019696:Peptidylprolyl Isomerase / Q000378:metabolism*; D010777:Photochemistry; D018272:Porins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D018271:Signal Recognition Particle / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; C068023:FtsQ protein, E coli; D008565:Membrane Proteins; D018272:Porins; D018271:Signal Recognition Particle; C082922:PhoE protein, E coli; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase