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Identification of novel tail-anchored membrane proteins integrated by the bacterial twin-arginine translocase

Lookup NU author(s): Dr Jose Gallego Parrilla, Dr Emmanuele SeveriORCiD, Professor Tracy Palmer FRS FRSE FMedSciORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2024 The Authors. The twin-arginine protein transport (Tat) system exports folded proteins across the cytoplasmic membranes of prokaryotes and the energy transducing-membranes of plant thylakoids and mitochondria. Proteins are targeted to the Tat machinery by N-terminal signal peptides with a conserved twin-arginine motif, and some substrates are exported as heterodimers where the signal peptide is present on one of the partner proteins. A subset of Tat substrates is found in the membrane. Tat-dependent membrane proteins usually have large globular domains and a single transmembrane helix present at the N-or C-terminus. Five Tat substrates that have C-terminal transmembrane helices have previously been characterized in the model bacterium Escherichia coli. Each of these is an iron–sulfur cluster-containing protein involved in electron transfer from hydrogen or formate. Here we have undertaken a bioinformatic search to identify further tail-anchored Tat substrates encoded in bacterial genomes. Our analysis has revealed additional tail-anchored iron–sulfur proteins associated in modules with either a b-type cytochrome or a quinol oxidase. We also identified further candidate tail-anchored Tat substrates, particularly among members of the actinobacterial phylum, that are not predicted to contain cofactors. Using reporter assays, we show experimentally that six of these have both N-terminal Tat signal peptides and C-terminal transmembrane helices. The newly identified proteins include a carboxypeptidase and a predicted protease, and four sortase substrates for which membrane integration is a prereq-uisite for covalent attachment to the cell wall.

Publication metadata

Author(s): Gallego-Parrilla JJ, Severi E, Chandra G, Palmer T

Publication type: Article

Publication status: Published

Journal: Microbiology

Year: 2024

Volume: 170

Issue: 2

Online publication date: 16/02/2024

Acceptance date: 22/01/2024

Date deposited: 05/03/2024

ISSN (print): 1350-0872

ISSN (electronic): 1465-2080

Publisher: Microbiology Society

URL: https://doi.org/10.1099/mic.0.001431

DOI: 10.1099/mic.0.001431

PubMed id: 38363712

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