Cloning the dapA dapB cluster of the lysine-secreting bacterium Corynebacterium glutamicum

Summary The genes encoding the two successive enzymes of the lysine biosynthetic pathway, dihydrodipicolinate synthase (dapA) and dihydrodipicolinate reductase (dapB), have been isolated from Corynebacterium glutamicum by heterologous complementation of Escherichia coli mutants. The two genes reside on a single 3.8-kb chromosomal fragment. They were subcloned as non overlapping fragments on an E. coli/C. glutamicum shuttle vector and introduced into C. glutamicum. This resulted in overexpression of both enzyme activities which was irrespective of the orientation of the inserts and comparable to that obtained with the large 3.8-kb fragment. Therefore, both genes are located in close proximity to each other on the C. glutamicum chromosome, but are apparently independently transcribed.