MOLECULAR ANALYSIS OF THE CORYNEBACTERIUM-GLUTAMICUM LYSL-GENE INVOLVED IN LYSINE UPTAKE

Two Corynebacterium glutamicum mutants defective in lysine uptake were identified by analysing mutants resistant to S-(2-aminoethyl)-cysteine (AEC). A 5.6 kb genomic DNA fragment restoring AEC sensitivity and lysine uptake was isolated. A 4.2 kb subfragment was sequenced and three open reading frames were identified. Subcloning and gene disruption experiments showed that only the first open reading frame, termed lysI, is involved in lysine uptake. LysI consists of 501 amino acids with a M(r) of 53600. The hydrophobicity profile suggests that the lysI gene product is an integral membrane protein with 13 transmembrane segments. The amino acid sequence of lysI displays strong homology to that of the arcD gene product of Pseudomonas aeruginosa, which is proposed to act as an arginine-ornithine antiporter. Investigation of the influence of the lysI gene on lysine secretion suggests the existence of a separate lysine efflux system in C. glutamicum.