A conserved extended signal peptide region directs posttranslational protein translocation via a novel mechanism

• Published in: Microbiology (Society for General Microbiology) Vol. 153; no. 1; pp. 59 - 70
• Main Authors: Desvaux, Mickael, Scott-Tucker, Anthony, Turner, Sue M, Cooper, Lisa M, Huber, Damon, Nataro, James P, Henderson, Ian R
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.01.2007; Society for General Microbiology; Microbiology Society
• Subjects: Amino Acid Sequence; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Cell Membrane - metabolism; Enterobacteriaceae; Enterobacteriaceae - metabolism; Fundamental and applied biological sciences. Psychology; Life Sciences; Microbiology; Microbiology and Parasitology; Molecular Sequence Data; Permeability, membrane transport, intracellular transport; Protein Biosynthesis; Protein Structure, Tertiary - physiology; Protein Transport; Serine Endopeptidases - chemistry; Serine Endopeptidases - metabolism; Leader peptide; Bacteria; Mechanism; Protein; Enterobacteriaceae; DEPENDENT TRANSLOCATION; BACTERIAL PATHOGENESIS; EXPORT; VIRULENCE FACTOR; INNER MEMBRANE TRANSLOCATION; SUBSET; SIGNAL PEPTIDE; GRAM-NEGATIVE BACTERIA; PATHWAY; AUTOTRANSPORTER PROTEINS; AUTOTRANSPORTER; TYPE V PROTEIN SECRETION SYSTEM; RECOGNITION PARTICLE; 2-PARTNER SECRETION; MEMBRANE-PROTEINS; ESCHERICHIA-COLI PERIPLASM
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.29091-0

1 Division of Immunity and Infection, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK 2 Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA 3 Center for Vaccine Development, University of Maryland, Baltimore, MD 21201, USA Correspondence Ian R. Henderson I.R.Henderson{at}bham.ac.uk Members of the type V secretion family are among the most prevalent secreted proteins in Gram-negative bacteria. A subset of this family, including Pet, the prototypical member of the Enterobacteriaceae serine proteases, possess unusual signal peptides which can be divided into five regions termed N1 (charged), H1 (hydrophobic), N2, H2 and C (cleavage site) domains. The N1 and H1 regions, which the authors have named the extended signal peptide region (ESPR), demonstrate remarkable conservation. In contrast, the N2, H2 and C regions show significant variability, and are reminiscent of typical Sec-dependent signal sequences. Despite several investigations, the function of the ESPR remains obscure. Here, it is shown that proteins possessing the ESPR are translocated in a posttranslational fashion. The presence of the ESPR severely impairs inner membrane translocation. Mutational analysis suggests that the ESPR delays inner membrane translocation by adopting a particular conformation, or by interacting with a cytoplasmic or inner membrane co-factor, prior to inner membrane translocation. Abbreviations: EP-PCR, error-prone PCR; ESPR, extended signal peptide region; FHA, filamentous haemagglutinin; SPATE, serine protease autotransporter of the Enterobacteriaceae ; SRP, signal recognition particle; T5SS, type V secretion system; TU, translocation unit; XP, 5-bromo-4-chloro-3-indolyl phosphate Present address: Institut National de la Recherche Agronomique (INRA), Centre de Recherche Clermont-Ferrand – Theix – Lyon, UR 454 – Unité de Microbiologie, Site de Theix, F-63122 Saint-Genès Champanelle, France.