HxcQ Liposecretin Is Self-piloted to the Outer Membrane by Its N-terminal Lipid Anchor

Secretins are an unusual and important class of bacterial outer membrane (OM) proteins. They are involved in the transport of single proteins or macromolecular structures such as pili, needle complexes, and bacteriophages across the OM. Secretins are multimeric ring-shaped structures that form large...

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Bibliographic Details
Published in:The Journal of biological chemistry 2009-12, Vol.284 (49), p.33815-33823
Main Authors: Viarre, Véronique, Cascales, Eric, Ball, Geneviève, Michel, Gérard P.F., Filloux, Alain, Voulhoux, Romé
Format: Article
Language:English
Subjects:
Bacterial Outer Membrane Proteins - chemistry
Bacterial Outer Membrane Proteins - metabolism
Biological Transport
Centrifugation, Density Gradient
Detergents - pharmacology
Escherichia coli
Escherichia coli - metabolism
Life Sciences
Lipids - chemistry
Lipoproteins - chemistry
Membrane Transport, Structure, Function, and Biogenesis
Palmitic Acid - chemistry
Peptides - chemistry
Plasmids - chemistry
Protein Structure, Tertiary
Pseudomonas aeruginosa
Pseudomonas aeruginosa - metabolism
Secretin - chemistry
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Summary:Secretins are an unusual and important class of bacterial outer membrane (OM) proteins. They are involved in the transport of single proteins or macromolecular structures such as pili, needle complexes, and bacteriophages across the OM. Secretins are multimeric ring-shaped structures that form large pores in the OM. The targeting of such macromolecular structures to the OM often requires special assistance, conferred by specific pilotins or pilot proteins. Here, we investigated HxcQ, the OM component of the second Pseudomonas aeruginosa type II secretion system. We found that HxcQ forms high molecular mass structures resistant to heat and SDS, revealing its secretin nature. Interestingly, we showed that HxcQ is a lipoprotein. Construction of a recombinant nonlipidated HxcQ (HxcQnl) revealed that lipidation is essential for HxcQ function. Further phenotypic analysis indicated that HxcQnl accumulates as multimers in the inner membrane of P. aeruginosa, a typical phenotype observed for secretins in the absence of their cognate pilotin. Our observations led us to the conclusion that the lipid anchor of HxcQ plays a pilotin role. The self-piloting of HxcQ to the OM was further confirmed by its correct multimeric OM localization when expressed in the heterologous host Escherichia coli. Altogether, our results reveal an original and unprecedented pathway for secretin transport to the OM.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M109.065938