L. Axelsson et al., CLONING AND NUCLEOTIDE-SEQUENCE OF A GENE FROM LACTOBACILLUS-SAKE LB706 NECESSARY FOR SAKACIN-A PRODUCTION AND IMMUNITY, Applied and environmental microbiology, 59(9), 1993, pp. 2868-2875
Sakacin A is an antilisterial bacteriocin produced by Lactobacillus sa
ke Lb706. In order to identify genes involved in sakacin A production
and immunity, the plasmid fraction of L. sake Lb706 was shotgun cloned
directly into a sakacin A-nonproducing and -sensitive variant, L. sak
e Lb706-B, by using the broad-host-range vector pVS2. Two clones that
produced sakacin A and were immune to the bacteriocin were obtained. A
DNA fragment of approximately 1.8 kb, derived from a 60-kb plasmid of
strain Lb706 and present in the inserts of both clones, was necessary
for restoration of sakacin A production and immunity in strain Lb706-
B. The sequence of the 1.8-kb fragment from one of the clones was dete
rmined. It contained one large open reading frame, designated sakB, po
tentially encoding a protein of 430 amino acid residues. Hybridization
and nucleotide sequence analyses revealed that the cloned sakB comple
mented a mutated copy of sakB present in strain Lb706-B. The sakB gene
mapped 1.6 kb from the previously cloned structural gene for sakacin
A (sakA) on the 60-kb plasmid. The putative SakB protein shared 22% am
ino acid sequence identity (51% similarity if conservative changes are
considered) to AgrB, the deduced amino acid sequence of the Staphyloc
occus aureus gene agrB. The polycistronic agr (accessory gene regulato
r) locus is involved in the regulation of exoprotein synthesis in S. a
ureus. Similar to the AgrB protein, SakB had some features in common w
ith a family of transmembrane histidine protein kinases, involved in v
arious adaptive response systems of bacteria. This similarity included
transmembrane regions in the N-terminal half of the protein and certa
in conserved amino acid residues.