Turnover of endogenous SsrA-tagged proteins mediated by ATP-dependent proteases in Escherichia coli.
J Biol Chem
; 283(34): 22918-29, 2008 Aug 22.
Article
em En
| MEDLINE
| ID: mdl-18550539
ABSTRACT
Formation and degradation of SsrA-tagged proteins enable ribosome recycling and elimination of defective products of incomplete translation. We produced an antibody against the SsrA peptide and used it to measure the amounts of SsrA-tagged proteins in Escherichia coli cells without interfering with tagging or altering the context of the tag added at the ends of nascent polypeptides. SsrA-tagged proteins were present in very small amounts unless a component of the ClpXP protease was missing. From the levels of tagged proteins in cells in which degradation is essentially blocked, we calculate that > or =1 in 200 translation products receives an SsrA tag. ClpXP is responsible for > or =90% of the degradation of SsrA-tagged proteins. The degradation rate in wild type cells is > or =1.4 min(-1) and decreases to approximately 0.10 min(-1) in a clpX mutant. The rate of degradation by ClpXP is decreased approximately 3-fold in mutants lacking the adaptor SspB, whereas degradation by ClpAP is increased 3-5-fold. However, ClpAP degrades SsrA-tagged proteins slowly even in the absence of SspB, possibly because of interference from ClpA-specific substrates. Lon protease degrades SsrA-tagged proteins at a rate of approximately 0.05 min(-1) in the presence or absence of SspB. We conclude that ClpXP, together with SspB, is uniquely adapted for degradation of SsrA-tagged proteins and is responsible for the major part of their degradation in vivo.
Texto completo:
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
RNA Bacteriano
/
Regulação Bacteriana da Expressão Gênica
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Trifosfato de Adenosina
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Escherichia coli
Idioma:
En
Ano de publicação:
2008
Tipo de documento:
Article