Plasmid pSM19035, a model to study stable maintenance in Firmicutes.

摘要: pSM19035 is a low-copy-number theta-replicating plasmid, which belongs to the Inc18 family. Plasmids of this family, show modular organization, are functional in evolutionarily diverse bacterial species Firmicutes Phylum. This review summarizes our understanding, accumulated during last 20 years, on genetics, biochemistry, cytology and physiology five segregation (seg) loci, map outside minimal replicon. The segA locus plays role both maximizing plasmid random segregation, avoiding replication fork collapses those plasmids with long inverted repeated regions. segB1 locus, acts as ultimate determinant maintenance, encodes short-lived epsilon(2) antitoxin protein long-lived zeta toxin protein, form complex that neutralizes toxicity. cells do not receive copy halt their proliferation upon decay antitoxin. segB2 two trans-acting, ParA- ParB-like proteins six cis-acting parS centromeres, actively ensures equal or roughly distribution copies daughter cells. segC includes functions promote shift from use DNA polymerase I replicase (PolC-PolE polymerases). segD trans-acting transcriptional repressor, omega(2), cognate sites, coordinates expression genes control number, better-than-random partition, assures proper balance these different functions. Working concert loci achieve almost absolute maintenance growth penalty.