Appl Environ Microbiol. 2014 Jun 20. pii: AEM.01370-14. [Epub ahead of print]
LacR is a repressor of lacABCD and LacT an activator of lacTFEG, constituting the lac-gene cluster in Streptococcus pneumoniae.
Afzal M1, Shafeeq S2, Kuipers OP3.
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Abstract
Transcriptome comparison of the Streptococcus pneumoniae strain D39 grown in the presence of either lactose or galactose with that of the strain grown in the presence of glucose, revealed the elevated expression of various genes and operons, including the lac gene cluster that is organized into two operons i.e. lac operon-I (lacABCD) and lac operon-II (lacTFEG). Deletion of the DeoR family transcriptional regulator lacR that is present downstream of the lac gene cluster, revealed elevated expression of lac operon-I, even in the absence of lactose. This suggests a function of LacR as a transcriptional repressor of lac operon-I that encodes enzymes involved in the Tagatose-6-P pathway in the absence of lactose or galactose. Deletion of lacR did not affect the expression of lac operon-II that encodes for a lactose-specific PTS. This finding was further confirmed by β-galactosidase assays with PlacA-lacZ and PlacT-lacZ in the presence of either lactose or glucose as a sole carbon source in the medium. This suggests the presence of another transcriptional regulator in the regulation of lac operon-II, which could be the BglG-family transcriptional antiterminator LacT. We demonstrate the role of LacT as a transcriptional activator of lac operon-II in the presence of lactose and CcpA-independent regulation of the lac gene cluster in S. pneumoniae.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
PMID: 24951784 [PubMed - as supplied by publisher]
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