Dataset Information

The membrane proteins SiaQ and SiaM form an essential stoichiometric complex in the sialic acid tripartite ATP-independent periplasmic (TRAP) transporter SiaPQM (VC1777-1779) from Vibrio cholerae.

ABSTRACT: Tripartite ATP-independent periplasmic (TRAP) transporters are widespread in bacteria but poorly characterized. They contain three subunits, a small membrane protein, a large membrane protein, and a substrate-binding protein (SBP). Although the function of the SBP is well established, the membrane components have only been studied in detail for the sialic acid TRAP transporter SiaPQM from Haemophilus influenzae, where the membrane proteins are genetically fused. Herein, we report the first in vitro characterization of a truly tripartite TRAP transporter, the SiaPQM system (VC1777-1779) from the human pathogen Vibrio cholerae. The active reconstituted transporter catalyzes unidirectional Na(+)-dependent sialic acid uptake having similar biochemical features to the orthologous system in H. influenzae. However, using this tripartite transporter, we demonstrate the tight association of the small, SiaQ, and large, SiaM, membrane proteins that form a 1:1 complex. Using reconstituted proteoliposomes containing particular combinations of the three subunits, we demonstrate biochemically that all three subunits are likely to be essential to form a functional TRAP transporter.

SUBMITTER: Mulligan C

PROVIDER: S-EPMC3271013 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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The membrane proteins SiaQ and SiaM form an essential stoichiometric complex in the sialic acid tripartite ATP-independent periplasmic (TRAP) transporter SiaPQM (VC1777-1779) from Vibrio cholerae.

Mulligan Christopher C Leech Andrew P AP Kelly David J DJ Thomas Gavin H GH

The Journal of biological chemistry 20111213 5

Tripartite ATP-independent periplasmic (TRAP) transporters are widespread in bacteria but poorly characterized. They contain three subunits, a small membrane protein, a large membrane protein, and a substrate-binding protein (SBP). Although the function of the SBP is well established, the membrane components have only been studied in detail for the sialic acid TRAP transporter SiaPQM from Haemophilus influenzae, where the membrane proteins are genetically fused. Herein, we report the first in vi ...[more]

PMID: 22167185

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Project description:The ability to efficiently scavenge nutrients in the host is essential for the viability of any pathogen. All catabolic pathways must begin with the transport of substrate from the environment through the cytoplasmic membrane, a role executed by membrane transporters. Although several classes of cytoplasmic membrane transporters are described, high-affinity uptake of substrates occurs through Solute Binding-Protein (SBP) dependent systems. Three families of SBP dependant transporters are known; the primary ATP-binding cassette (ABC) transporters, and the secondary Tripartite ATP-independent periplasmic (TRAP) transporters and Tripartite Tricarboxylate Transporters (TTT). Far less well understood than the ABC family, the TRAP transporters are found to be abundant among bacteria from marine environments, and the TTT transporters are the most abundant family of proteins in many species of ?-proteobacteria. In this review, recent knowledge about these families is covered, with emphasis on their physiological and structural mechanisms, relating to several examples of relevant uptake systems in pathogenicity and colonization, using the SiaPQM sialic acid uptake system from Haemophilus influenzae and the TctCBA citrate uptake system of Salmonella typhimurium as the prototypes for the TRAP and TTT transporters, respectively. High-throughput analysis of SBPs has recently expanded considerably the range of putative substrates known for TRAP transporters, while the repertoire for the TTT family has yet to be fully explored but both types of systems most commonly transport carboxylates. Specialized spectroscopic techniques and site-directed mutagenesis have enriched our knowledge of the way TRAP binding proteins capture their substrate, while structural comparisons show conserved regions for substrate coordination in both families. Genomic and protein sequence analyses show TTT SBP genes are strikingly overrepresented in some bacteria, especially in the ?-proteobacteria and some ?-proteobacteria. The reasons for this are not clear but might be related to a role for these proteins in signaling rather than transport.

Dataset Information

The membrane proteins SiaQ and SiaM form an essential stoichiometric complex in the sialic acid tripartite ATP-independent periplasmic (TRAP) transporter SiaPQM (VC1777-1779) from Vibrio cholerae.

Publications

The membrane proteins SiaQ and SiaM form an essential stoichiometric complex in the sialic acid tripartite ATP-independent periplasmic (TRAP) transporter SiaPQM (VC1777-1779) from Vibrio cholerae.

Similar Datasets

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