title: Signal recognition particle (SRP)-mediated targeting and Sec-dependent translocation of an extracellular Escherichia coli protein.
abstract: Hemoglobin protease (Hbp) is a hemoglobin-degrading protein that is secreted by a human pathogenic Escherichia coli strain via the autotransporter mechanism. Little is known about the earliest steps in autotransporter secretion, i.e. the targeting to and translocation across the inner membrane. Here, we present evidence that Hbp interacts with the signal recognition particle (SRP) and the Sec-translocon early during biogenesis. Furthermore, Hbp requires a functional SRP targeting pathway and Sec-translocon for optimal translocation across the inner membrane. SecB is not required for targeting of Hbp but can compensate to some extent for the lack of SRP. Hbp is synthesized with an unusually long signal peptide that is remarkably conserved among a subset of autotransporters. We propose that these autotransporters preferentially use the co-translational SRP/Sec route to avoid adverse effects of the exposure of their mature domains in the cytoplasm.
authors.affiliation: Department of Molecular Microbiology, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.
authors.forename: Robert
authors.initials: R
authors.lastname: Sijbrandi
authors.forename: Malene L
authors.initials: ML
authors.lastname: Urbanus
authors.forename: Corinne M
authors.initials: CM
authors.lastname: ten Hagen-Jongman
authors.forename: Harris D
authors.initials: HD
authors.lastname: Bernstein
authors.forename: Bauke
authors.initials: B
authors.lastname: Oudega
authors.forename: Ben R
authors.initials: BR
authors.lastname: Otto
authors.forename: Joen
authors.initials: J
authors.lastname: Luirink
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D021381:Protein Transport / Q000235:genetics; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D018271:Signal Recognition Particle / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D018271:Signal Recognition Particle; D010450:Endopeptidases; C114676:hemoglobin protease Hbp; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins