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

NorM, a putative efflux pump of Vibrio cholerae, is a member of the multidrug and toxic compound extrusion family of transporters. We demonstrate that NorM confers resistance to norfloxacin, ciprofloxacin, and ethidium bromide. Inactivation of norM rendered V. cholerae hypersensitive towards these fluoroquinolones. Multiple sequence alignment of members of its family identified several regions of high sequence conservation. The topology of NorM was determined using beta-lactamase and chloramphenicol acetyltransferase fusions. The amino acid residues G(184), K(185), G(187), P(189), E(190), G(192), and G(195) in the periplasmic loops and L(381), R(382), G(383), Y(384), K(385), and D(386) in the cytoplasmic loops, as well as all the acidic and cysteine residues of NorM, were mutated. Mutants G184V, G184W, K185I, P189S, E190K, and E190A lost the norfloxacin resistance-imparting phenotype characteristic of NorM. Mutants E124V, D155V, G187V, G187R, C196S, Y384H, Y384S, and Y384F exhibited partial resistance to norfloxacin. Mutants with replacements of G(184) or G(187) by A, K(185) by R, and E(190) by D retained the norfloxacin resistance phenotype of NorM. Analysis of the accumulation of norfloxacin in intact cells of Escherichia coli expressing NorM or its mutants in the presence or absence of carbonyl cyanide m-chlorophenylhydrazone supported the results obtained through susceptibility testing and argued in favor of NorM-mediated efflux as the determining factor in norfloxacin susceptibility in the genetically manipulated strains. Taken together, these results suggested that E(124), D(155), G(184), K(185), G(187), P(189), E(190), C(196), and Y(384) are likely involved in NorM-dependent norfloxacin efflux. Except for D(155), C(196), and Y(384), all of these residues are located in periplasmic loops.
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PMID:Analysis of the topology of Vibrio cholerae NorM and identification of amino acid residues involved in norfloxacin resistance. 1695 25

Brome mosaic virus (BMV) is a plant virus whose genome consists of three RNA components. A previously described viral complementary DNA expression system has been used to express both wild-type and altered genomic RNA's in barley protoplasts. Variants of BMV RNA3 were constructed in which the coat gene had been removed or replaced with sequences encoding chloramphenicol acetyltransferase (CAT). CAT sequences were also inserted near the 5' end of the intact coat gene. When inoculated on protoplasts together with transcripts of BMV RNA's 1 and 2, all of these RNA3 derivatives were replicated and produced subgenomic RNA's analogous to the normal subgenomic coat protein messenger RNA. RNA3 derivatives in which the CAT coding sequences were oriented with the same polarity as viral genes produced significant CAT activity in protoplasts. CAT expression was improved by inserting the CAT gene in frame with the upstream coat protein initiation codon, and exceeded expression in plant cells transformed with Ti plasmid-based vectors.
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PMID:Bacterial gene inserted in an engineered RNA virus: efficient expression in monocotyledonous plant cells. 1783 68


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