Document Detail


Hydrogen peroxide and coffee induce G:C-->T:A transversions in the lacI gene of catalase-defective Escherichia coli.
MedLine Citation:
PMID:  10474829     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The mutagenicity of hydrogen peroxide (H2O2) was compared with that of coffee, a complex mixture which generates H2O2. An Escherichia coli strain defective in catalase activity (katG katE double mutant) and carrying a single copy mucAB (pRW144) plasmid was constructed to enhance the mutagenic response to oxidants. The ability of the mucAB genes to influence the type, frequency and distribution of H2O2-induced mutations was also investigated in isogenic bacteria lacking pRW144. Induced mutational spectra were characterized and compared with that of spontaneous mutagenesis. A total of 444 independent forward mutations affecting the first 210 bp of the lacI gene were identified by DNA sequence analysis. The spontaneous mutation spectrum showed no bias (P = 0.52) for substitutions at G:C base pairs. In contrast, in the H2O2-induced spectrum substitutions occurred preferentially at G:C base pairs (P < 0.0001) with a preponderance of G:C-->T:A transversions (43.4% of H2O2-induced mutants versus 17.3% of spontaneous mutants). These data support the view that 7,8-dihydro-8-oxoguanine is the main premutagenic lesion induced by H2O2 and that catalase-defective bacteria have elevated levels of 8-oxoguanine in chromosome DNA after H2O2 exposure. Coffee produced a similar distribution of mutational events as H2O2 (P > 0.05), suggesting that this compound may be the main cause of the coffee-induced mutagenesis. The presence of plasmid pRW144 did not affect the frequency of H2O2-induced G:C-->T:A transversions, but caused an increase in A:T-->T:A transversions and a decrease in -1 base frameshifts. Although the frequencies of G:C-->T:A transversions were similar in all three induced spectra (H2O2 and coffee +/- pRW144), differences were observed in location of mutations throughout the target gene.
Authors:
J Ruiz-Laguna; C Pueyo
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Mutagenesis     Volume:  14     ISSN:  0267-8357     ISO Abbreviation:  Mutagenesis     Publication Date:  1999 Jan 
Date Detail:
Created Date:  1999-10-08     Completed Date:  1999-10-08     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  8707812     Medline TA:  Mutagenesis     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  95-102     Citation Subset:  IM    
Affiliation:
Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, España.
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MeSH Terms
Descriptor/Qualifier:
Acatalasia*
Bacterial Proteins / genetics
Base Sequence
Coffee / toxicity*
DNA Mutational Analysis
Escherichia coli / drug effects*,  enzymology,  genetics*
Escherichia coli Proteins*
Hydrogen Peroxide / toxicity*
Lac Operon / drug effects*
Lac Repressors
Molecular Sequence Data
Mutagens / toxicity*
Mutation / drug effects,  genetics
Point Mutation / drug effects,  genetics
Repressor Proteins / genetics
Chemical
Reg. No./Substance:
0/Bacterial Proteins; 0/Coffee; 0/Escherichia coli Proteins; 0/Lac Repressors; 0/LacI protein, E coli; 0/Mutagens; 0/Repressor Proteins; 7722-84-1/Hydrogen Peroxide

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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