非表示:
キーワード:
programmed cell death;varε protein; ζ protein; toxin inactivation; phosphotransferase
要旨:
Programmed cell death in prokaryotes is frequently found as postsegregational killing. It relies on antitoxin/toxin systems that secure stable inheritance of low and medium copy number plasmids during cell division and kill cells that have lost the plasmid. The broad-host-range, low-copy-number plasmid pSM19035 from Streptococcus pyogenes carries the genes encoding the antitoxin/toxin system ɛ/ζ and antibiotic resistance proteins, among others. The crystal structure of the biologically nontoxic ɛ2ζ2 protein complex at a 1.95-Å resolution and site-directed mutagenesis showed that free ζ acts as phosphotransferase by using ATP/GTP. In ɛ2ζ2, the toxin ζ is inactivated because the N-terminal helix of the antitoxin ɛ blocks the ATP/GTP-binding site. To our knowledge, this is the first prokaryotic postsegregational killing system that has been entirely structurally characterized.
