Genetic and biochemical analysis of the aspartokinase from Corynebacterium glutamicum

Abstract

The lysC/asd gene cluster of Corynebacterium glutamicum ATCC 13032 was cloned and sequenced. The lysC locus coding for aspartokinase consists of two in‐frame overlapping genes, lysCα encoding a protein of 421 amino acids (M_r 44300) and lysCβ encoding a protein of 172 amino acids (M_r 18600). The C. glutamicum aspartokinase was purified and found to contain two proteins of M_r 47000 and M_r 18000. A C. glutamicum mutant expressing a feedback‐resistant aspartokinase was shown to be changed in a single base pair of the lysCβ gene, leading to an amino acid exchange in the β‐subunit of the aspartokinase. In addition, the identified mutation was found to be responsible for the enhanced expression of the asd gene located downstream of lysC.