Biochemical characterization of a chromosomal toxin–antitoxin system in Mycobacterium tuberculosis

In the present paper, we report the biochemical characterization of a chromosomal toxin–antitoxin (TA) system in Mycobacterium tuberculosis, consisting of the Rv1991c gene and its upstream open reading frame (ORF) termed Rv1991a. Rv1991c was characterized as a toxin with ribonuclease activity and Rv1991a as the antitoxin against Rv1991c. Rv1991a interacted with Rv1991c to form a complex. A promoter located immediately upstream of Rv1991a was identified. Both Rv1991a and the Rv1991a–Rv1991c complex were able to bind to the promoter region of the Rv1991a–Rv1991c operon, indicating that the expression of the Rv1991a–Rv1991c operon can be autoregulated.