Structural and functional characterization of SiiA, an auxiliary protein from the SPI4-encoded type 1 secretion system from Salmonella enterica

Kirchweger P, Weiler S, Egerer-Sieber C, Blasl AT, Hoffmann S, Schmidt C, Sander N, Merker D, Gerlach R, Hensel M, Muller Y (2019)

Publication Type: Journal article

Publication year: 2019

Journal

Molecular Microbiology Wiley-Blackwell

DOI: 10.1111/mmi.14368

Abstract

Salmonella invasion is mediated by a concerted action of the Salmonella pathogenicity island 4 (SPI4)-encoded type one secretion system (T1SS) and the SPI1-encoded type three secretion system (T3SS-1). The SPI4-encoded T1SS consists of five proteins (SiiABCDF) and secretes the giant adhesin SiiE. Here, we investigated structure-function relationships in SiiA, a non-canonical T1SS subunit. We show that SiiA consists of a membrane domain, an intrinsically disordered periplasmic linker region and a folded globular periplasmic domain (SiiA-PD). The crystal structure of SiiA-PD displays homology to that of MotB and other peptidoglycan (PG)-binding domains. SiiA-PD binds PG in vitro, albeit at an acidic pH, only. Mutation of Arg162 impedes PG binding of SiiA and reduces Salmonella invasion efficacy. SiiA forms a complex with SiiB at the inner membrane (IM), and the observed SiiA-MotB homology is paralleled by a predicted SiiB-MotA homology. We show that, similar to MotAB, SiiAB translocates protons across the IM. Mutating Asp13 in SiiA impairs proton translocation. Overall, SiiA shares numerous properties with MotB. However, MotAB uses the proton motif force (PMF) to energize the bacterial flagellum, it remains to be shown how usage of the PMF by SiiAB assists T1SS function and Salmonella invasion.

Authors with CRIS profile

Peter Kirchweger Lehrstuhl für Biotechnik (Proteinstruktur und -design) Sigrid Weiler Lehrstuhl für Biotechnik (Proteinstruktur und -design) Anna-Theresa Blasl Professur für Computational Biology Roman Gerlach Institute of Microbiology – Clinical Microbiology, Immunology and Hygiene Yves Muller Lehrstuhl für Biotechnik (Proteinstruktur und -design)

Involved external institutions

Robert Koch-Institut (RKI) DE Germany (DE) Universität Osnabrück DE Germany (DE)

How to cite

APA:

Kirchweger, P., Weiler, S., Egerer-Sieber, C., Blasl, A.-T., Hoffmann, S., Schmidt, C.,... Muller, Y. (2019). Structural and functional characterization of SiiA, an auxiliary protein from the SPI4-encoded type 1 secretion system from Salmonella enterica. Molecular Microbiology. https://doi.org/10.1111/mmi.14368

MLA:

Kirchweger, Peter, et al. "Structural and functional characterization of SiiA, an auxiliary protein from the SPI4-encoded type 1 secretion system from Salmonella enterica." Molecular Microbiology (2019).

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