A mutation in the Corynebacterium glutamicum ItsA gene causes susceptibility to lysozyme, temperature-sensitive growth, and L-glutamate production

The Corynebacterium glutamicum mutant KY9714, originally isolated as a lyso zyme-sensitive mutant, does not grow at 37 degrees C. Complementation tests and DNA sequencing analysis revealed that a mutation in a single gene of 1 ,920 bp, ltsA (lysozyme and temperature sensitive), was responsible for its lysozyme sensitivity and temperature sensitivity. The ltsA gene encodes a protein homologous to the glutamine-dependent asparagine synthetases of var ious organisms, but it could not rescue the asparagine auxotrophy of an Esc herichia coli asnA asnB double mutant. Replacement of the N-terminal Cys re sidue (which is conserved in glutamine-dependent amidotransferases and is e ssential for enzyme activity) by an Ala residue resulted in the loss of com plementation in C. glutamicum. The mutant ltsA gene has an amber mutation, and the disruption of the ltsA gene caused lysozyme and temperature sensiti vity similar to that in the KY9714 mutant. L-Glutamate production was induc ed by elevating growth temperature in the disruptant. These results indicat e that the ltsA gene encodes a novel glutamine-dependent amidotransferase t hat is involved in the mechanisms of formation of rigid cell wall structure and in the L-glutamate production of C. glutamicum.