title: Crystal structure of the plasmid maintenance system epsilon/zeta: functional mechanism of toxin zeta and inactivation by epsilon 2 zeta 2 complex formation.
abstract: 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 epsilon/zeta and antibiotic resistance proteins, among others. The crystal structure of the biologically nontoxic epsilon(2)zeta(2) protein complex at a 1.95-A resolution and site-directed mutagenesis showed that free zeta acts as phosphotransferase by using ATPGTP. In epsilon(2)zeta(2), the toxin zeta is inactivated because the N-terminal helix of the antitoxin epsilon blocks the ATPGTP-binding site. To our knowledge, this is the first prokaryotic postsegregational killing system that has been entirely structurally characterized.
authors.affiliation: Institut für Kristallographie, Freie Universität Berlin, Takustrasse 6, D-14195 Berlin, Germany.
authors.forename: Anton
authors.initials: A
authors.lastname: Meinhart
authors.forename: Juan C
authors.initials: JC
authors.lastname: Alonso
authors.forename: Norbert
authors.initials: N
authors.lastname: Sträter
authors.forename: Wolfram
authors.initials: W
authors.lastname: Saenger
mesh_terms: D000595:Amino Acid Sequence; D000992:Antitoxins / Q000494:pharmacology; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009876:Operon; D010957:Plasmids; D011487:Protein Conformation; D017510:Protein Folding; D017386:Sequence Homology, Amino Acid; D013297:Streptococcus pyogenes / Q000737:chemistry*
chemical_list: D000992:Antitoxins; D001427:Bacterial Toxins