Characterization of a unique mutant lysE gene, originating from Corynebacterium glutamicum, encoding a product that induces L-lysine production in Methylophilus methylotrophus

lysE24 is an allele of lysE encoding an L-lysine exporter of Corynebacterium glutamicum. The mutant gene is able to induce L-lysine production in Methylophilus methylotrophus. Although lysE24 has a mutation in the middle of lysE that results in chain termination, the entire lysE locus, including the region downstream of the short open reading frame, is necessary for L-lysine production. We propose that separate polypeptides are synthesized from the lysE24 locus due to reinitiation of translation utilizing an existing start codon beyond the site of the frameshift, and present evidence that translational coupling is required to form the functional lysE24 product. In addition, expression of lysE24 induces L-lysine production in another methylotroph, Methylobacillus glycogenes. These data suggest that the lysE24 product is a split protein and that this curious feature might be a structure necessary for its functioning in certain obligate gram-negative methylotrophs.