Biochemical and structural characterization of a DNA N6-adenine methyltransferas

来源:中国生理学会基质生物学专业委员会    添加时间:2017-04-03 13:58:41
Biochemical and structural characterization of a DNA N6-adenine methyltransferase from Helicobacter pylori

B. Ma, J. Ma, D. Liu, L. Guo, H. Chen, J. Ding, W. Liu, H. Zhang*

Oncotarget, 7 (2016) 40965-40977. 

DNA N6-methyladenine modification plays an important role in regulating a variety of biological functions in bacteria. However, the mechanism of sequence-specific recognition in N6-methyladenine modification remains elusive. M1.HpyAVI, a DNA N6-adenine methyltransferase from Helicobacter pylori, shows more promiscuous substrate specificity than other enzymes. Here, we present the crystal structures of cofactor-free and AdoMet-bound structures of this enzyme, which were determined at resolutions of 3.0 Å and 3.1 Å, respectively. The core structure of M1.HpyAVI resembles the canonical AdoMet-dependent MTase fold, while the putative DNA binding regions considerably differ from those of the other MTases, which may account for the substrate promiscuity of this enzyme. Site-directed mutagenesis experiments identified residues D29 and E216 as crucial amino acids for cofactor binding and the methyl transfer activity of the enzyme, while P41, located in a highly flexible loop, playing a determinant role for substrate specificity. Taken together, our data revealed the structural basis underlying DNA N6-adenine methyltransferase substrate promiscuity.


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