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J. Bacteriol., 04 1995, 2125-2137, Vol 177, No. 8
L Axelsson and A Holck
Sakacin A is a small, heat-stable, antilisterial bacteriocin produced by
Lactobacillus sake Lb706. The nucleotide sequence of a 8,668-bp fragment,
shown to contain all information necessary for sakacin A production and
immunity, was determined. The sequence revealed the presence of two
divergently transcribed operons. The first encompassed the structural gene
sapA (previously designated sakA) and saiA, which encoded a putative
peptide of 90 amino acid residues. The second encompassed sapK (previously
designated sakB), sapR, sapT, and sapE. sapK and sapR presumably encoded a
histidine kinase and a response regulator with marked similarities to the
AgrB/AgrA type of two- component signal-transducing systems. The putative
SapT and SapE proteins shared similarity with the Escherichia coli
hemolysin A-like signal sequence-independent transport systems. SapT was
the HlyB analog with homology to bacterial ATP-binding cassette exporters
implicated in bacteriocin transport. Frameshift mutations and deletion
analyses showed that sapK and sapR were necessary for both production and
immunity, whereas sapT and sapE were necessary for production but not for
immunity. The putative SaiA peptide was shown to be involved in the
immunity to sakacin A. The region between the operons contained IS1163, a
recently described L. sake insertion element. IS1163 did not appear to be
involved in expression of the sap genes. Northern (RNA) blot analysis
revealed that the putative SapK/SapR system probably acts as a
transcriptional activator on both operons. A 35-bp sequence, present
upstream of the putative sapA promoter, and a similar sequence (30 of 35
nucleotides identical) upstream of sapK were shown to be necessary for
proper expression and could thus be possible targets for transcriptional
activation.
Copyright © 1995, American Society for Microbiology
The genes involved in production of and immunity to sakacin A, a bacteriocin from Lactobacillus sake Lb706
MATFORSK, Norwegian Food Research Institute, As.
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