Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

Human lymphoid cell lines contain a DNA repair enzyme which removes the mutagenic alkylation lesion O6-methylguanine from DNA. The enzyme transfers the methyl group to a protein cysteine residue, generating S-methylcysteine, and is inactivated as a consequence of the reaction. Apparently the methylated enzyme represents a dead-end complex. The transfer reaction is very rapid and is completed in less than 1 min at 37 degrees, but methyl group transfer from single-stranded DNA or heavily damaged DNA is less efficient. The active methyltransferase and the methylated protein both have molecular weights of 21,000 to 22,000, as determined by gel filtration. Lymphoid cell lines proficient in repair of O6-methylguanine in vivo, Mex+, contain 10,000 to 25,000 molecules of the methyltransferase per cell. In contrast, repair-deficient cell lines, Mex-, do not contain detectable amounts of the enzyme. The latter point was verified by applying a partial purification procedure for the enzyme to cell-free extracts from two Mex- cell lines.

Type

Journal article

Journal

Cancer Res

Publication Date

07/1983

Volume

43

Pages

3247 - 3252

Keywords

Burkitt Lymphoma, Cell Extracts, Cell Line, Chromatography, Gel, DNA Glycosylases, DNA Repair, Escherichia coli, Humans, Kinetics, Lymphocytes, Methyltransferases, Molecular Weight, N-Glycosyl Hydrolases, O(6)-Methylguanine-DNA Methyltransferase, Phenotype, Xeroderma Pigmentosum