期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：4
页码：1661-1666
DOI：10.1073/pnas.0434325100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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 {varepsilon}/{zeta} and antibiotic resistance proteins, among others. The crystal structure of the biologically nontoxic {varepsilon}2{zeta}2 protein complex at a 1.95-A resolution and site-directed mutagenesis showed that free {zeta} acts as phosphotransferase by using ATP/GTP. In {varepsilon}2{zeta}2, the toxin {zeta} is inactivated because the N-terminal helix of the antitoxin {varepsilon} blocks the ATP/GTP-binding site. To our knowledge, this is the first prokaryotic postsegregational killing system that has been entirely structurally characterized.
