Structure and expression of the overlapping genes for the subunits of Bacillus sahtilis aspartokinase II

Abstract

Aspartokmase II of Bacillus subtilis is composed of two nonidentical subunits, a and b, arranged in an x,O, structure The two subunits are encoded by in-phase overlapping genes, which constitute a single operon. The promoter overlaps an adjacent open reading frame and is followed by an extensive leader sequencc that appears to function as a transcription attenuator. The transcription terminator of the aspartokinase II operon is shared with a converging transcription unit. The translation initiation sites of the aspartokinase II a and B subunits were defined by sequence analysis and site-directed mutagenesis. The study of specific deletion, frame-shift, and missense mutations clearly demonstrated that the aspartokinase II subunits are translated independently from overlapping genes.