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Recognition and selectivity of peptide pheromones by ComR in the regulation of natural competence among Streptococcus species
Author(s) -
Prehna Gerd,
Shanker Erin,
Morrison Donald A,
Talagas Antoine,
Nessler Sylvie,
Federle Michael J
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.621.1
Subject(s) - quorum sensing , biology , peptide , signal peptide , biochemistry , receptor , peptide sequence , gene , genetics , response regulator , computational biology , alanine scanning , virulence , mutagenesis , microbiology and biotechnology , mutant
Bacteria transmit chemical signals to each other in a process known as quorum sensing. This adaptation is central to pathogenesis as it allows bacteria to coordinate a group response, such as when to secrete virulence factors or uptake new DNA. Quorum sensing in many species of Gram‐positive bacteria utilizes secreted short peptide signals that are sensed by protein receptors that alter gene expression. The ComR‐ComS receptor‐signal pair is a regulator of competence for genetic transformation that is broadly conserved in a majority of Streptococcus species. Despite this conservation, we observe sequence diversity among ComRS orthologs that raises questions relating to sensory specificity, potential cross‐talk between species, and the molecular mechanism of peptide recognition. To address this, we developed a ‘test‐bed’ assay to measure the activity of ComR proteins in response to cognate and heterologous XIP (mature ComS) peptides in vivo. This led to the identification of three categories of ComR receptors displaying strict, modest, and promiscuous responses. To elucidate the molecular mechanism of receptor specificity we determined an x‐ray crystal structure of ComR in the apo‐conformation and probed the XIP binding pocket by site‐directed mutagenesis both in test‐bed cultures and biochemically in vitro. From the structural and biochemical data, we observe a conserved face of the ligand pocket important for peptide binding and a variable face that functions in peptide specificity. Finally, the basic criteria necessary for peptide responses were used to redesign active peptides from inactive templates. Together, our results provide a model for XIP recognition and specificity, and serves as a template for the generation of novel XIP peptides. Support or Funding Information This work was supported by NIH grant R01‐AI091779 to MJF, Burroughs Wellcome Fund, NIH Fellowship 5F30AI110080 to ES, and funding provided by the University of Illinois at Chicago, Research Resources Center.