title: Deoxyribonucleic acid modification methylase from Bacillus stearothermophilus.
abstract: A modification methylase was isolated from Bacillus stearothermophilus 1503-4R (Bst 1503I) and purified to homogeneity. The enzyme is an acidic protein and composed of a subunit with a molecular weight of 105 000, and only the tetrameric form was detected in solution. The methylase exhibited maximal activity between 54 and 61 degrees C and between pH 8.1 and 9.3. In contrast to Bst 1503I endonuclease [Catterall, J.F., & Welker, N. E. (1977) J. Bacteriol. 129, 1110-1120], the methylase is completely inactivated when exposed to temperatures near the optimal growth temperature (63-67 degrees C). The methylase was also inactivated when exposed to temperatures below the minimal growth temperature (48-53 degrees C). The thermostability of the methylase is significantly enhanced by Na+, K+, or NH4+. Membrane-bound methylase is resistant to heat inactivation at temperatures near the maximum growth temperature (73-75 degrees C). The methylase functions as a tetramer. The initial rates of methyl transfer are first order in methylase concentration, and the enzyme obeys Michaelis-Menten kinetics with respect to DNA but not to S-adenosyl-L-methionine.
mesh_terms: D001426:Bacterial Proteins; D002414:Cations, Monovalent; D015257:DNA-Cytosine Methylases; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D007700:Kinetics; D046911:Macromolecular Substances; D008780:Methyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D012436:S-Adenosylmethionine / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D002414:Cations, Monovalent; D046911:Macromolecular Substances; D012436:S-Adenosylmethionine; C030019:DNA modification methylase Bst15031; D015257:DNA-Cytosine Methylases; D008780:Methyltransferases