期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1994
卷号：91
期号：23
页码：10957-10961
DOI：10.1073/pnas.91.23.10957
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The Thermus aquaticus DNA methyltransferase M.Taq I (EC 2.1.1.72 ) methylates N6 of adenine in the specific double-helical DNA sequence TCGA by transfer of --CH3 from the cofactor S-adenosyl-L-methionine. The x-ray crystal structure at 2.4-A resolution of this enzyme in complex with S-adenosylmethionine shows alpha/beta folding of the polypeptide into two domains of about equal size. They are arranged in the form of a C with a wide cleft suitable to accommodate the DNA substrate. The N-terminal domain is dominated by a nine-stranded beta-sheet; it contains the two conserved segments typical for N-methyltransferases which form a pocket for cofactor binding. The C-terminal domain is formed by four small beta-sheets and alpha-helices. The three-dimensional folding of M.Taq I is similar to that of the cytosine-specific Hha I methyltransferase, where the large beta-sheet in the N-terminal domain contains all conserved segments and the enzymatically functional parts, and the smaller C-terminal domain is less structured.
