Limited tolerance towards folded elements during secretion of the autotransporter Hbp.

W.S.P. Jong, C.M. ten Hagen-Jongman ten, T. den Blaauwen, D.J. Slotboom, J.R.H. Tame, D. Wickstrom, J.-W. de Gier, B.R. Otto, S. Luirink

Research output: Contribution to JournalArticleAcademic

Abstract

Many virulence factors secreted by pathogenic Gram-negative bacteria belong to the autotransporter (AT) family. ATs consist of a passenger domain, which is the actual secreted moiety, and a β-domain that facilitates the transfer of the passenger domain across the outer membrane. Here, we analysed folding and translocation of the AT passenger, using Escherichia coli haemoglobin protease (Hbp) as a model protein. Dual cysteine mutagenesis, instigated by the unique crystal structure of the Hbp passenger, resulted in intramolecular disulphide bond formation dependent on the periplasmic enzyme DsbA. A small loop tied off by a disulphide bond did not interfere with secretion of Hbp. In contrast, a bond between different domains of the Hbp passenger completely blocked secretion resulting in degradation by the periplasmic protease DegP. In the absence of DegP, a translocation intermediate accumulated in the outer membrane. A similar jammed intermediate was formed upon insertion of a calmodulin folding moiety into Hbp. The data suggest that Hbp can fold in the periplasm but must retain a certain degree of flexibility and/or modest width to allow translocation across the outer membrane. © 2007 The Authors.
Original languageEnglish
Pages (from-to)1524-1536
JournalMolecular Microbiology
Volume63
Issue number5
DOIs
Publication statusPublished - 2007

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