Two operons that encode FNR-like proteins in Lactococcus lactis.
Global regulatory circuits of the type mediated by CRP and FNR in Escherichia coli were sought in Lactococcus lactis to provide a basis for redirecting carbon metabolism to specific fermentation products. Using a polymerase chain reaction (PCR) approach, two genes (flpA and flpB) encoding FNR-like proteins (FlpA and FlpB) with the potential for mediating a dithiol-disulphide-dependent regulatory switch, were identified. Transcript analysis indicated that they are distal genes of two paralogous operons, orfX-orfY-flp, in which the orfX and orfY genes were predicted to encode binding domain components of cation ATPases and storage proteins respectively. The corresponding promoters were each associated with a potential FNR site (TTGAT----ATCAA) at positions +4.5 (flpA operon) and -42.5 (flpB operon), suggesting that the respective operons might be negatively and positively autoregulated. The incomplete open reading frames (orfWA/B) located upstream of each operon were predicted to encode additional components of paralogous cation ATPases. No phenotypic effects were detected in flpA and flpB single mutants, but the double mutant had a lower intracellular zinc content, an increased sensitivity to hydrogen peroxide and an altered polypeptide profile (as determined by two-dimensional gel electrophoresis): formate production was not affected. It was concluded tentatively that FlpA and FlpB regulate overlapping modulons, including systems concerned with zinc uptake, in response to metal ion or oxidative stress.
Gostick
D O
DO
Department of Molecular Biology and Biotechnology, University of Sheffield, UK.
Griffin
H G
HG
Shearman
C A
CA
Scott
C
C
Green
J
J
Gasson
M J
MJ
Guest
J R
JR
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D015153:Blotting, Western; D004254:DNA Nucleotidyltransferases / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins / Q000235:genetics*; D013294:Lactococcus lactis / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009876:Operon; D010455:Peptides / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; C119770:FlpA protein, bacteria; C119771:FlpB protein, Lactococcus lactis; D007506:Iron-Sulfur Proteins; D010455:Peptides; D014157:Transcription Factors; D004254:DNA Nucleotidyltransferases; C045119:FLP recombinase