Properties of human O/sup 6/-methylguanine-DNA methyltransferase

Conference · Fri May 01 04:00:00 EDT 1987 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:6025575

Bhattacharyya, D; Boulden, A M; Foote, R S; Mitra, S

The premutagenic base, O/sup 6/-methylguanine, is repaired in the DNA of both bacterial and mammalian cells by stoichiometric transfer of the methyl group to a protein cysteine residue. The human O/sup 6/-methylguanine-DNA methyltransferase has been extensively purified from placenta and partially characterized with respect to reaction kinetics, pH and temperature dependencies, and the effects of salt, metal ions, and DNA concentration. The methyl-transfer reaction has apparent second-order kinetics and an energy of activation, calculated from temperature-dependence studies, of approximately 18 kcal. The reaction rate is optimal at a pH of about 8.5. Chromatofocusing experiments indicate a pI of 6.2 for the methyltransferase. Like the E. coli and rodent methyltransferases, the human protein has no cofactor requirements. The reaction is significantly inhibited by physiological concentrations of NaCl. Both single- and double-stranded DNA also inhibit the reaction, presumably by nonspecific binding of the protein. Changes in the human methyltransferase due to its reaction with O/sup 6/-methylguanine were examined by chromatofocusing and binding to DNA-cellulose. The results were compared with those obtained in parallel experiments using purified methyltransferase from E. coli.

• Research Organization: Oak Ridge National Lab., TN
• OSTI ID: 6025575
• Report Number(s): CONF-870644-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 46:6
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BACTERIA
BIOCHEMICAL REACTION KINETICS
CHEMICAL PROPERTIES
COMPARATIVE EVALUATIONS
DNA
ENZYMES
ESCHERICHIA COLI
KINETICS
MAMMALS
MAN
MICROORGANISMS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PH VALUE
PRIMATES
REACTION KINETICS
STOICHIOMETRY
TEMPERATURE DEPENDENCE
TRANSFERASES
VERTEBRATES