Pheromone Recognition and Selectivity by ComR Proteins among Streptococcus Species

Journal Article · Thu Dec 01 00:00:00 EST 2016 · PLoS Pathogens

DOI:https://doi.org/10.1371/journal.ppat.1005979· OSTI ID:1498415

Shanker, Erin  ^[1]; Morrison, Donald A. ^[1]; Talagas, Antoine ^[2]; Nessler, Sylvie ^[2]; Federle, Michael J. ^[1]; Prehna, Gerd ^[1]; Zhang, Gongyi ^[3]

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1. Univ. of Illinois, Chicago, IL (United States)
2. Univ. Paris-Sud, Univ. Paris-Saclay (France)
3. National Jewish Health, Denver, CO (United States)

Natural transformation, or competence, is an ability inherent to bacteria for the uptake of extracellular DNA. This process is central to bacterial evolution and allows for the rapid acquirement of new traits, such as antibiotic resistance in pathogenic microorganisms. For the Gram-positive bacteria genus Streptococcus, genes required for competence are under the regulation of quorum sensing (QS) mediated by peptide pheromones. One such system, ComRS, consists of a peptide (ComS) that is processed (XIP), secreted, and later imported into the cytoplasm, where it binds and activates the transcription factor ComR. ComR then engages in a positive feedback loop for the expression of ComS and the alternative sigma-factor SigX. Although ComRS are present in the majority of Streptococcus species, the sequence of both ComS/XIP and ComR diverge significantly, suggesting a mechanism for species-specific communication. To study possible cross-talk between streptococcal species in the regulation of competence, and to explore in detail the molecular interaction between ComR and XIP we undertook an interdisciplinary approach. We developed a ‘test-bed’ assay to measure the activity of different ComR proteins in response to cognate and heterologous XIP peptides in vivo, revealing distinct ComR classes of strict, intermediate, and promiscuous specificity among species. We then solved an X-ray crystal structure of ComR from S. suis to further understand the interaction with XIP and to search for structural features in ComR proteins that may explain XIP recognition. Using the structure as a guide, we probed the apo conformation of the XIP-binding pocket by site-directed mutagenesis, both in test-bed cultures and biochemically in vitro. In alignments with ComR proteins from other species, we find that the pocket is lined by a variable and a conserved face, where residues of the conserved face contribute to ligand binding and the variable face discriminate among XIP peptides. Together, our results not only provide a model for XIP recognition and specificity, but also allow for the prediction of novel XIP peptides that induce ComR activity.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National Inst. of Health; Burroughs Wellcome Fund; Michigan Economic Development Corp.; Michigan Technology Tri-Corridor
• Grant/Contract Number: AC02-06CH11357; AI091779; 5F30AI110080; 085P1000817
• OSTI ID: 1498415
• Journal Information: PLoS Pathogens, Vol. 12, Issue 12; ISSN 1553-7374
• Publisher: Public Library of Science
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
Streptococcus mutans
pheromones
crystal structure
Streptococcus suis
Streptococcus agalactiae
Streptococcus pyogenes
face recognition
sequence motif analysis