Genetic organization of the mle locus and identification of a mleR-like gene from Leuconostoc oenos

The characterization of the mle locus from Leuconostoc oenos shows a 2.6-kb transcript, indicating that it may have an operon structure containing the malolactic enzyme gene mleA and malate permease gene mleP. The mle operon has one transcription start site situated 17 nucleotides upstream of the ATG translation start site for the mleA gene. An 894-bp open reading frame (RF), that transcribes divergently from the mle operon, is located upstream of the mleA gene. This ORF encodes a polypeptide belonging to the LysR-type regulatory protein family, and has a molecular mass of 34 kDa.