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Cloning and sequence analysis of putative histidine protein kinases isolated from Lactococcus lactis MG1363.

ABSTRACT: Eight recombinant plasmids harboring chromosomal fragments of Lactococcus lactis MG1363 were shown to phenotypically suppress a histidine protein kinase (HPK) deficiency in either of two different E. coli strains. Sequence analysis of the plasmid inserts revealed five different complete or partial open reading frames (ORFs) specifying proteins with high similarity to HPKs. One of the plasmids also harbored an additional ORF, unrelated to HPKs, with suppressing activity.

SUBMITTER: O'Connell-Motherway M

PROVIDER: S-EPMC168540 | biostudies-other | 1997 Jun

REPOSITORIES: biostudies-other

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Cloning and sequence analysis of putative histidine protein kinases isolated from Lactococcus lactis MG1363.

O'Connell-Motherway M M Fitzgerald G F GF van Sinderen D D

Applied and environmental microbiology 19970601 6

Eight recombinant plasmids harboring chromosomal fragments of Lactococcus lactis MG1363 were shown to phenotypically suppress a histidine protein kinase (HPK) deficiency in either of two different E. coli strains. Sequence analysis of the plasmid inserts revealed five different complete or partial open reading frames (ORFs) specifying proteins with high similarity to HPKs. One of the plasmids also harbored an additional ORF, unrelated to HPKs, with suppressing activity. ...[more]

PMID: 9172368

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Project description:In Lactococcus lactis, the his operon contains all the genes necessary for histidine biosynthesis. It is transcribed from a unique promoter, localized 300 bp upstream of the first gene. The region corresponding to the untranslated 5' end of the transcript, named the his leader region, displays the typical features of the T box transcriptional attenuation mechanism which is involved in the regulation of many amino acid biosynthetic operons and tRNA synthetase genes in gram-positive bacteria. Here we describe the regulation of transcription of the his operon by the level of histidine in the growth medium. In the absence of histidine, two transcripts are present. One covers the entire operon, while the other stops at a terminator situated about 250 bp downstream of the transcription start point. DNA sequences implicated in regulation of the his operon were identified by transcriptional fusion with luciferase genes and site-directed mutagenesis. In addition to the previously defined sequences necessary for effective T-box-mediated regulation, new essential regions were identified. Eighteen percent of the positions of the his leader region were found to differ in seven distantly related strains of L. lactis. Analysis of the variable positions supports the folding model of the central part of the his leader region. Lastly, in addition to the T-box-mediated regulation, the operon is regulated at the level of initiation of transcription, which is repressed in the presence of histidine. An operator site, necessary for full repression, overlaps the terminator involved in the T box attenuation mechanism. The functionality of the operator is altered on plasmids with low and high copy numbers, suggesting that supercoiling may play a role in the expression of the his operon. The extents of regulation at the levels of initiation and attenuation of transcription are 6- to 8-fold and 14-fold, respectively. Together, the two levels of control allow a 120-fold range of regulation of the L. lactis operon by histidine.

Dataset Information

Cloning and sequence analysis of putative histidine protein kinases isolated from Lactococcus lactis MG1363.

Publications

Cloning and sequence analysis of putative histidine protein kinases isolated from Lactococcus lactis MG1363.

Similar Datasets

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