Interactions of CcdB with DNA gyrase. Inactivation of Gyra, poisoning of the gyrase-DNA complex, and the antidote action of CcdA.
J Biol Chem
; 274(16): 10936-44, 1999 Apr 16.
Article
em En
| MEDLINE
| ID: mdl-10196173
ABSTRACT
The F plasmid-carried bacterial toxin, the CcdB protein, is known to act on DNA gyrase in two different ways. CcdB poisons the gyrase-DNA complex, blocking the passage of polymerases and leading to double-strand breakage of the DNA. Alternatively, in cells that overexpress CcdB, the A subunit of DNA gyrase (GyrA) has been found as an inactive complex with CcdB. We have reconstituted the inactive GyrA-CcdB complex by denaturation and renaturation of the purified GyrA dimer in the presence of CcdB. This inactivating interaction involves the N-terminal domain of GyrA, because similar inactive complexes were formed by denaturing and renaturing N-terminal fragments of the GyrA protein in the presence of CcdB. Single amino acid mutations, both in GyrA and in CcdB, that prevent CcdB-induced DNA cleavage also prevent formation of the inactive complexes, indicating that some essential interaction sites of GyrA and of CcdB are common to both the poisoning and the inactivation processes. Whereas the lethal effect of CcdB is most probably due to poisoning of the gyrase-DNA complex, the inactivation pathway may prevent cell death through formation of a toxin-antitoxin-like complex between CcdB and newly translated GyrA subunits. Both poisoning and inactivation can be prevented and reversed in the presence of the F plasmid-encoded antidote, the CcdA protein. The products of treating the inactive GyrA-CcdB complex with CcdA are free GyrA and a CcdB-CcdA complex of approximately 44 kDa, which may correspond to a (CcdB)2(CcdA)2 heterotetramer.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
/
Toxinas Bacterianas
/
DNA
/
DNA Topoisomerases Tipo II
/
Citotoxinas
/
Inibidores da Topoisomerase II
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
1999
Tipo de documento:
Article