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J Bacteriol

Title:		The HtrA protease of Streptococcus pneumoniae controls density-dependent stimulation of the bacteriocin blp locus via disruption of pheromone secretion
Author(s):		Kochan TJ; Dawid S;
Address:		"Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, MI, USA"
Journal Title:		J Bacteriol
Year:		2013
Volume:		20130125
Issue:		7
Page Number:		1561 - 1572
DOI:		10.1128/JB.01964-12
ISSN/ISBN:		1098-5530 (Electronic) 0021-9193 (Print) 0021-9193 (Linking)
Abstract:		"All fully sequenced strains of Streptococcus pneumoniae (pneumococcus) contain a version of the blp locus which is responsible for the regulation and secretion of a variable repertoire of pneumococcal bacteriocins called pneumocins and their associated immunity proteins. Pneumocins mediate intra- and interspecies competition in vitro and have been shown to provide a competitive advantage in vivo. Pneumocin production is stimulated by extracellular accumulation of the peptide pheromone, BlpC. Both BlpC and the functional pneumocins are secreted out of the cell via the Blp transporter, BlpAB. The conserved surface-expressed serine protease, HtrA, has been shown to limit activation of the locus and secretion of functional pneumocins. In this work, we demonstrate that htrA mutants stimulate the blp locus at lower cell density and to a greater extent than strains expressing wild-type HtrA. This effect is not due to direct proteolytic degradation of secreted pheromone by the protease, but instead is a result of HtrA-mediated disruption of peptide processing and secretion. Because pneumocins are secreted through the same transporter as the pheromone, this finding explains why pheromone supplementation cannot completely restore pneumocin inhibition to strains expressing high levels of HtrA despite restoration of blp transcriptional activity. HtrA restricts pneumocin production to high cell density by limiting the rate of accumulation of BlpC in the environment. Importantly, HtrA does not interfere with the ability of a strain to sense environmental pheromones, which is necessary for the induction of protective immunity in the face of pneumocin-secreting competitors"
Keywords:		"Bacteriocins/*metabolism *Gene Expression Regulation, Bacterial Membrane Transport Proteins/*metabolism Pheromones/*metabolism Serine Endopeptidases/*metabolism Streptococcus pneumoniae/*enzymology/*genetics;"
Notes:		"MedlineKochan, Travis J Dawid, Suzanne eng R01 AI078538/AI/NIAID NIH HHS/ R01 AI101285/AI/NIAID NIH HHS/ AI078538/AI/NIAID NIH HHS/ Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't 2013/01/29 J Bacteriol. 2013 Apr; 195(7):1561-72. doi: 10.1128/JB.01964-12. Epub 2013 Jan 25"