Affordable Access

Co-dependent positive regulation of the ansB promoter of Escherichia coli by CRP and the FNR protein: a molecular analysis.

Authors
Type
Published Article
Journal
Molecular Microbiology
0950-382X
Publisher
Wiley Blackwell (Blackwell Publishing)
Publication Date
Volume
9
Issue
1
Pages
155–164
Identifiers
PMID: 8412660
Source
Medline

Abstract

Transcription of the ansB gene, encoding L-asparaginase II, is positively regulated by cAMP receptor protein (CRP) and by the product of the fnr gene, the FNR protein. These global regulatory proteins mediate the expression of ansB in Escherichia coli in response to carbon source and to anaerobiosis, respectively, and are required concurrently for optimal ansB expression. The mechanism whereby CRP and FNR interact co-operatively with the ansB promoter to achieve transcription has not previously been established. We have utilized an ansB'-'lacZ fusion, in conjunction with deletion analysis and site-directed mutagenesis, to identify two sites which interact with these regulatory proteins in the ansB promoter. The first is an FNR site, centred 41.5 bp upstream of the major transcriptional start site. The second site, located 28 bp upstream of the FNR site, is the site of CRP regulation. This site is homologous to both the CRP and FNR binding-site consensus sequences and may respond to both CRP and FNR. The concurrent requirement for CRP and FNR for optimal expression of ansB may be explained if, first, essentially no transcription occurs unless the FNR is bound at the downstream site, and, second, the level of transcription when FNR alone is present is enhanced when CRP binds at the upstream site.

There are no comments yet on this publication. Be the first to share your thoughts.

Statistics

Seen <100 times
0 Comments
F