Glycine acylation and trafficking of a new class of bacterial lipoprotein by a composite secretion system

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Abstract

Protein acylation is critical for many cellular functions across all domains of life. In bacteria, lipoproteins have important roles in virulence and are targets for the development of antimicrobials and vaccines. Bacterial lipoproteins are secreted from the cytosol via the Sec pathway and acylated on an N-terminal cysteine residue through the action of three enzymes. In Gram-negative bacteria, the Lol pathway transports lipoproteins to the outer membrane. Here we demonstrate that the Aat secretion system is a composite system sharing similarity with elements of a type I secretion systems and the Lol pathway. During secretion, the AatD subunit acylates the substrate CexE on a highly conserved N-terminal glycine residue. Mutations disrupting glycine acylation interfere with membrane incorporation and trafficking. Our data reveal CexE as the first member of a new class of glycine-acylated lipoprotein, while Aat represents a new secretion system that displays the substrate lipoprotein on the cell surface.

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All data generated or analysed during this study are included in the manuscript and supporting files

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Christopher Icke

Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-7815-8591
Freya J Hodges

Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia

Competing interests
The authors declare that no competing interests exist.
Karthik Pullela

Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia

Competing interests
The authors declare that no competing interests exist.
Samantha A McKeand

Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Jack Alfred Bryant

Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-7912-2144
Adam F Cunningham

Institute of Microbiology and Infection, Institute of Inflammation and Immunotherapy, University of Birmingham, Birmingham, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Jeff A Cole

Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Ian R Henderson

Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia

For correspondence
i.henderson@imb.uq.edu.au

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-9954-4977

Funding

Biotechnology and Biological Sciences Research Council (DTP)

Adam F Cunningham
Ian R Henderson

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.