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Structural and biophysical analysis of a Haemophilus influenzae tripartite ATP-independent periplasmic (TRAP) transporter
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. University of Canterbury, New Zealand.ORCID iD: 0000-0003-4029-1650
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.ORCID iD: 0000-0003-0960-994x
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Number of Authors: 192024 (English)In: eLIFE, E-ISSN 2050-084X, Vol. 12, article id RP92307Article in journal (Refereed) Published
Abstract [en]

Tripartite ATP-independent periplasmic (TRAP) transporters are secondary-active transporters that receive their substrates via a soluble-binding protein to move bioorganic acids across bacterial or archaeal cell membranes. Recent cryo-electron microscopy (cryo-EM) structures of TRAP transporters provide a broad framework to understand how they work, but the mechanistic details of transport are not yet defined. Here we report the cryo-EM structure of the Haemophilus influenzae N-acetylneuraminate TRAP transporter (HiSiaQM) at 2.99 Å resolution (extending to 2.2 Å at the core), revealing new features. The improved resolution (the previous HiSiaQM structure is 4.7 Å resolution) permits accurate assignment of two Na+ sites and the architecture of the substrate-binding site, consistent with mutagenic and functional data. Moreover, rather than a monomer, the HiSiaQM structure is a homodimer. We observe lipids at the dimer interface, as well as a lipid trapped within the fusion that links the SiaQ and SiaM subunits. We show that the affinity (KD) for the complex between the soluble HiSiaP protein and HiSiaQM is in the micromolar range and that a related SiaP can bind HiSiaQM. This work provides key data that enhances our understanding of the ‘elevator-with-an-operator’ mechanism of TRAP transporters.

Place, publisher, year, edition, pages
2024. Vol. 12, article id RP92307
Keywords [en]
sialic acid, Neu5Ac, protein-protein interaction, membrane transport proteins, transport mechanism, Other
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:su:diva-227954DOI: 10.7554/eLife.92307ISI: 001162186400001PubMedID: 38349818Scopus ID: 2-s2.0-85182017089OAI: oai:DiVA.org:su-227954DiVA, id: diva2:1850049
Available from: 2024-04-09 Created: 2024-04-09 Last updated: 2024-04-09Bibliographically approved

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Davies, James S.Gulati, AshutoshDrew, DavidNorth, Rachel A.

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Currie, Michael J.Davies, James S.Gulati, AshutoshNewton-Vesty, Michael C.Griffin, Michael D. W.Wakatsuki, SoichiDrew, DavidNorth, Rachel A.
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