The Cysteine Protease MaOC1, a Prokaryotic Caspase Homolog, Cleaves the Antitoxin of a Type II Toxin-Antitoxin System.

摘要: The bloom-forming cyanobacterium Microcystis aeruginosa is known for its global distribution and the production of toxic compounds. In genome M. PCC 7806, we discovered that gene coding MaOC1, a caspase homologue protease, followed by toxin-antitoxin module, flanked on each side direct repeat. We therefore investigated their possible interaction at protein level. Our results suggest this module belongs to ParE/ParD-like superfamily type II systems. solution, antitoxin predominantly alpha-helical dimeric. When coexpressed with cognate toxin isolated from Escherichia coli, it forms complex, as revealed multi-angle light scattering affinity purification. active site restricted C-terminus molecule. Its truncation led normal cell growth, while wild-type form prevented bacterial growth in liquid medium. orthocaspase MaOC1 was able cleave so could no longer block activity. most likely target protease two sections basic amino acid residues. E. coli cells which expressed simultaneously pair were unable grow. contrast, effect found when using proteolytically inactive mutant. thus present first case cysteine regulates activity since all currently activating proteases are serine type.