title: Structure of HsdS subunit from Thermoanaerobacter tengcongensis sheds lights on mechanism of dynamic opening and closing of type I methyltransferase.
abstract: Type I DNA methyltransferases contain one specificity subunit (HsdS) and two modification subunits (HsdM). The electron microscopy model of M.EcoKI-M₂S₁ methyltransferase shows a reasonable closed state of this clamp-like enzyme, but the structure of the open state is still unclear. The 1.95 Å crystal structure of the specificity subunit from Thermoanaerobacter tengcongensis (TTE-HsdS) shows an unreported open form inter-domain orientation of this subunit. Based on the crystal structure of TTE-HsdS and the closed state model of M.EcoKI-M₂S₁, we constructed a potential open state model of type I methyltransferase. Mutational studies indicated that two α-helices (aa30-59 and aa466-495) of the TTE-HsdM subunit are important inter-subunit interaction sites in the TTE-M₂S₁ complex. DNA binding assays also highlighted the importance of the C-terminal region of TTE-HsdM for DNA binding by the TTE-M₂S₁ complex. On the basis of structural analysis, biochemical experiments and previous studies, we propose a dynamic opening and closing mechanism for type I methyltransferase.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Pu
authors.initials: P
authors.lastname: Gao
authors.forename: Qun
authors.initials: Q
authors.lastname: Tang
authors.forename: XiaoMin
authors.initials: X
authors.lastname: An
authors.forename: XiaoXue
authors.initials: X
authors.lastname: Yan
authors.forename: DongCai
authors.initials: D
authors.lastname: Liang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D015280:DNA Restriction-Modification Enzymes / Q000737:chemistry* / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D008780:Methyltransferases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism; D046968:Thermoanaerobacter / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D015280:DNA Restriction-Modification Enzymes; D004269:DNA, Bacterial; C113046:HSDS protein, Bacteria; D021122:Protein Subunits; D008780:Methyltransferases