Importation of nuclease colicins into E coli cells: endoproteolytic cleavage and its prevention by the immunity protein.
Biochimie
; 84(5-6): 423-32, 2002.
Article
em En
| MEDLINE
| ID: mdl-12423785
ABSTRACT
A major group of colicins comprises molecules that possess nuclease activity and kill sensitive cells by cleaving RNA or DNA. Recent data open the possibility that the tRNase colicin D, the rRNase colicin E3 and the DNase colicin E7 undergo proteolytic processing, such that only the C-terminal domain of the molecule, carrying the nuclease activity, enters the cytoplasm. The proteases responsible for the proteolytic processing remain unidentified. In the case of colicin D, the characterization of a colicin D-resistant mutant shows that the inner membrane protease LepB is involved in colicin D toxicity, but is not solely responsible for the cleavage of colicin D. The lepB mutant resistant to colicin D remains sensitive to other colicins tested (B, E1, E3 and E2), and the mutant protease retains activity towards its normal substrates. The cleavage of colicin D observed in vitro releases a C-terminal fragment retaining tRNase activity, and occurs in a region of the amino acid sequence that is conserved in other nuclease colicins, suggesting that they may also require a processing step for their cytotoxicity. The immunity proteins of both colicins D and E3 appear to have a dual role, protecting the colicin molecule against proteolytic cleavage and inhibiting the nuclease activity of the colicin. The possibility that processing is an essential step common to cell killing by all nuclease colicins, and that the immunity protein must be removed from the colicin prior to processing, is discussed.
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Coleções:
01-internacional
Contexto em Saúde:
3_ND
Base de dados:
MEDLINE
Assunto principal:
Peptídeo Hidrolases
/
Proteínas de Bactérias
/
Colicinas
/
Proteínas de Escherichia coli
/
Escherichia coli
/
Proteínas de Membrana
Idioma:
En
Revista:
Biochimie
Ano de publicação:
2002
Tipo de documento:
Article