Journal Article

Functional interactions between homologous conditional killer systems of plasmid and chromosomal origin

Sandra Santos-Sierra, Rafael Giraldo and Ramón Díaz-Orejas

in FEMS Microbiology Letters

Volume 152, issue 1, pages 51-56
Published in print July 1997 |
Published online January 2006 | e-ISSN: 1574-6968 | DOI:

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parD and chpA are homologous conditional killer systems of plasmid and chromosomal origin, respectively, encoding a killer protein (Kid and ChpAK) and an antidote (Kis and ChpAI). Here it is shown that these systems can functionally interact. A multicopy chpA recombinant partially complements two mutations in the antidote of the parD system. These mutations affect either autoregulation or neutralization of the killer component. Following in vitro mutagenesis with hydroxylamine, chpA mutants that improve this complementation were isolated. Sequence analysis shows that these mutants are clustered in the 5′ end of the chpAI gene and structure predictions suggest that they affect a putative loop in the secondary structure of the ChpAI antidote. It is proposed that this region is part of a protein-protein interface required for the functional interaction between the antidote and the killer components in the two homologous systems.

Keywords: parD operon; chpA operon; Conditional killer system; Plasmid stability; chpAI mutant; chpA and parD interaction

Journal Article.  2739 words.  Illustrated.

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