Open AccessSwitching Control of Expression of ptsG from the Mlc Regulon to the NagC Regulon
Author(s) -
Samir El Qaidi,
Jacqueline Plumbridge
Publication year - 2008
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00315-08
Subject(s) - regulon , biology , repressor , operator (biology) , gene , genetics , regulation of gene expression , gene expression
The Mlc and NagC transcriptional repressors bind to similar 23-bp operators. The sequences are weakly palindromic, with just four positions totally conserved. There is no cross regulation observed between the repressors in vivo, but there are no obvious bases which could be responsible for operator site discrimination. To investigate the basis for operator recognition and to try to understand what differentiates NagC sites from Mlc sites, we have undertaken mutagenesis experiments to convertptsG from a gene regulated by Mlc into a gene regulated by NagC. There are two Mlc operators upstream ofptsG , and to switchptsG to the NagC regulon, it was necessary to change two different characteristics of both operators. Firstly, we replaced the AT base pair at position +/−11 from the center of symmetry of the operators with a GC base pair. Secondly, we changed the sequence of the CG base pairs in the central region of the operator (positions −4 to +4 around the center of symmetry). Our results show that changes at either of these locations are sufficient to lose regulation by Mlc but that both types of changes in both operators are necessary to convertptsG to a gene regulated by NagC. In addition, these experiments confirmed that two operators are necessary for regulation by NagC. We also show that regulation ofptsG by Mlc involves some cooperative binding of Mlc to the two operators.