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Appl. Environ. Microbiol., 12 1996, 4493-4498, Vol 62, No. 12
C Labarre, C Divies and J Guzzo
Characterization of the mle locus harboring the malolactic enzyme gene mleA
and malate permease gene mleP from Leuconostoc oenos was completed in this
study by mRNA analysis. Northern (RNA) blot experiments revealed a 2.6-kb
transcript, suggesting an operon structure harboring mleA and mleP genes.
Primer extension analysis showed that the mle operon has a single
transcription start site located 17 nucleotides upstream of the ATG
translation start site for the mleA gene. We found sequences, TTGACT and
TATGAT (which are separated by 18 bp), that are closely related to the
gram-positive and Escherichia coli consensus promoter sequences. Upstream
of the mleA gene, an 894-bp open reading frame that transcribed divergently
from the mle operon was found. Sequence analysis and expression in E. coli
minicells suggest that this open reading frame encodes a polypeptide with
an apparent molecular mass of 34 kDa belonging to the LysR-type regulatory
protein family. Protein comparisons showed the highest level of identity
with the MleR regulatory protein from Lactococcus lactis, which is involved
in the expression of the malolactic genes in the presence of L-malate.
However, the MleR-like protein of L. oenos seems different from the protein
of Lactococcus lactis, since no regulation of the malolactic enzyme by
L-malate was effective under our experimental conditions.
Copyright © 1996, American Society for Microbiology
Genetic organization of the mle locus and identification of a mleR-like gene from Leuconostoc oenos
Laboratorie de Microbiologie, Ecole Nationale Superieure de Biologie Appliquee a la Nutrition et a l'Alimentation, Dijon, France.
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