Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A trimeric enzyme chloramphenicol acetyltransferase (CATI) has been synthesized in the Zubay system genetically depleted from DnaK and DnaJ. Most of CAT formed in the system fail to assemble into an active trimer. Instead CAT is accumulated in either a GroEL-bound complex or as an inactive monomer. Addition of purified DnaK and DnaJ to the system prior to the start of protein synthesis leads to the increase of the specific activity of formed CAT. A portion of exogenous DnaK and DnaJ added to the system associate with nascent polypeptide chains in the ribosomes. DnaK also comigrates with 50S-ribosomal subunits.
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PMID:Synthesis of chloramphenicol acetyltransferase in a coupled transcription-translation in vitro system lacking the chaperones DnaK and DnaJ. 749 1

Recent evidence supports the view that cellular protein folding may be mediated by molecular chaperones. A fundamental question concerns the stage in its biogenesis at which the folding protein makes first contact with these components. We show here by crosslinking that the chaperone DnaJ binds nascent ribosome-bound polypeptide chains as short as 55 residues. Cotranslational binding of DnaJ to firefly luciferase and chloramphenicol acetyltransferase resulted in an arrest of folding as long as the functional partners of DnaJ in Escherichia coli, DnaK and GrpE, were missing. Protein uptake into microsomes and mitochondria was also interrupted by DnaJ. Both folding and post-translational translocation recommenced upon addition of DnaK and GrpE. We propose that DnaJ protects nascent polypeptide chains against aggregation and, in cooperation with Hsp70, controls their productive folding once a complete polypeptide or a polypeptide domain has been synthesized.
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PMID:Control of folding and membrane translocation by binding of the chaperone DnaJ to nascent polypeptides. 823 79

The role of two chaperone proteins, DnaK and the cooperating factor DnaJ, in Escherichia coli antibiotic susceptibility to three antibiotics (a beta-lactam, chloramphenicol, tetracycline) has been studied. It was found that null dnaJ and dnaKdnaJ mutants are impaired in the functions leading to antibiotic susceptibility. The secretion of beta-lactamase to the periplasmic space is diminished in both mutants, and the additive effect of the two mutations was observed. The activity of chloramphenicol acetyltransferase is also impaired in an additive manner in both mutant strains. Tetracycline uptake is changed only in the double deletion mutant. These defects were observed only during incubation at high temperature (42 degrees C). Efficient complementation of some of these defects by the wild-type alleles introduced on low-copy number plasmid was achieved. Minimal inhibitory concentrations and the titer of the wild-type strains, delta dnaJ and delta dnaKdnaJ mutants treated with ampicillin, chloramphenicol, and tetracycline were also determined. Higher susceptibility of both mutants to chloramphenicol and tetracycline, as compared to their wild-type parent, was observed only after 1 h preincubation of cultures at 42 degrees C. On the contrary, both mutants were less susceptible to ampicillin than their parent strain.
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PMID:Antibiotic susceptibility of Escherichia coli dnaK and dnaJ mutants. 1099 Feb 66