title: DNA cytosine methylation and heat-induced deamination.
abstract: The heat-induced conversion of 5-methylcytosine (m5C) residues to thymine residues and of cytosine to uracil residues in single-stranded DNA was studied. The calculated rates for deamination at 37 degrees C and pH 7.4 were approximately 9.5 X 10(-10) and 2.1 X 10(-10) sec-1, respectively. N4-Methyldeoxycytidine, which is in the DNA of certain thermophilic bacteria, was more heat-resistant than was deoxycytidine and much more than was 5-methyldeoxycytidine. Thermophilic bacteria which contain N4-methylcytosine rather than m5C in their genomes may thereby largely avoid heat-induced mutation due to deamination, which is incurred by the many organisms that contain m5C in their DNA.
mesh_terms: D044503:5-Methylcytosine; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism*; D003641:Deamination; D004926:Escherichia coli / Q000235:genetics; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D008745:Methylation; D013941:Thymine / Q000378:metabolism; D014498:Uracil / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D014498:Uracil; D044503:5-Methylcytosine; D003596:Cytosine; D013941:Thymine