Previous Article | Next Article ![]()
J. Bacteriol., Mar 1997, 1555-1562, Vol 179, No. 5
CA Alpert and U Siebers
The 5' region of the lac operon of Lactobacillus casei has been
investigated. An open reading frame of 293 codons, designated lacT, was
identified upstream of lacE. The gene product encoded by lacT is related to
the family of transcriptional antiterminator proteins, which includes BglG
from Escherichia coli, ArbG from Erwinia chrysanthemi, SacT, SacY, and LicT
from Bacillus subtilis, and BglR from Lactococcus lactis. Amino acid
sequence identities range from 35 to 24%, while similarities range from 56
to 47%. The transcriptional start site of the lac operon was identified
upstream of lacT. The corresponding mRNA would contain in the 5' region a
sequence with high similarity to the consensus RNA binding site of
transcriptional antiterminators overlapping a sequence capable of folding
into a structure that resembles a rho-independent terminator. LacT was
shown to be active as an antiterminator in a B. subtilis test system using
the sacB target sequence. lacT directly precedes lacEGF, the genes coding
for enzyme IICB, phospho-beta-galactosidase, and enzyme IIA, and these
genes are followed by a sequence that appears to encode a second
rho-independent transcription terminator-like structure. Northern
hybridizations with probes against lacT, lacE, and lacF revealed
transcripts of similar sizes for the lac mRNAs of several L. casei strains.
Since the length of the lac mRNA is just sufficient to contain lacTEGF, we
conclude that the lac operon of L. casei does not contain the genes of the
accessory tagatose-6-phosphate pathway as occurs in the lac operons of
Lactococcus lactis, Streptococcus mutans, or Staphylococcus aureus.
Copyright © 1997, American Society for Microbiology
The lac operon of Lactobacillus casei contains lacT, a gene coding for a protein of the Bg1G family of transcriptional antiterminators
Fachbereich Biologie/Chemie, AG Genetik, Universitat Osnabruck, Germany. Alpert@wolf.biologie.uni-osnabrueck.de
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»