Identification of a Vibrio cholerae chemoreceptor that senses taurine and amino acids as attractants

Abstract

Vibrio cholerae, the etiological agent of cholera, was found to be attracted by taurine (2-aminoethanesulfonic acid), a major constituent of human bile. Mlp37, the closest homolog of the previously identified amino acid chemoreceptor Mlp24, was found to mediate taxis to taurine as well as L-serine, L-alanine, L-arginine, and other amino acids. Methylation of Mlp37 was enhanced upon the addition of taurine and amino acids. Isothermal titration calorimetry demonstrated that a purified periplasmic fragment of Mlp37 binds directly to taurine, L-serine, L-alanine and L-arginine. Crystal structures of the periplamic domain of Mlp37 revealed that L-serine and taurine bind to the membrane-distal PAS domain in essentially in the same way. The structural information was supported by characterising the in vivo properties of alanine-substituted mutant forms of Mlp37. The fact that the ligand-binding domain of the L-serine complex had a small opening, which would accommodate a larger R group, accounts for the broad ligand specificity of Mlp37 and allowed us to visualise ligand binding to Mlp37 with fluorescently labelled L-serine. Taken together, we conclude that Mlp37 serves as the major chemoreceptor for taurine and various amino acids.

Mutations in the β-Subunit of the RNA Polymerase Impair the Surface-Associated Motility and Virulence of Acinetobacter baumannii

“…Similarly, Vibrio cholerae possesses a chemoreceptor that mediates the response to taurine, a major constituent of human bile, and thus plays an important role in the chemotaxis and virulence of the pathogen (38). The A. baumannii RS14730 gene encodes a putative taurine ATP-binding transport system component involved in the transport of taurine as a sulfur source.…”

Transmembrane Signal Transduction in Two‐Component Systems: Piston, Scissoring, or Helical Rotation?

“…For several of TCS receptors, crystallographic structures, or other data on periplasmic domains are available, often in both ligand‐free (apo) and ligand‐bound (holo) states. The first example is the single‐pass HK BT4633, where binding of heparan sulfate‐derived disaccharide causes 15 Å scissor‐like displacement of C‐termini toward each other .…”

The periplasmic sensing domain of <i>Pseudomonas fluorescens </i>chemotactic transducer of amino acids type B (CtaB): Cloning, refolding, purification, crystallization, and X-ray crystallographic analysis

“…X-ray crystallographic analysis of CtaB PTPSD in complex with various amino acid ligands is expected to provide an explanation of the structural basis behind the broad ligand specificity of this receptor. We note that the crystal structure of PTPSD of another 'promiscuous' amino acid MCP receptor, V. cholerae Mcp37, has been recently reported (18). However, only the crystal complexes of that protein with alanine and serine have been characterised, which makes it difficult to predict how larger amino acids can fit into its relatively small ligand-binding pocket.…”