title: Structural insights into the mechanism and evolution of the vaccinia virus mRNA cap N7 methyl-transferase.
abstract: The vaccinia virus mRNA capping enzyme is a multifunctional heterodimeric protein associated with the viral polymerase that both catalyses the three steps of mRNA capping and regulates gene transcription. The structure of a subcomplex comprising the C-terminal N7-methyl-transferase (MT) domain of the large D1 subunit, the stimulatory D12 subunit and bound S-adenosyl-homocysteine (AdoHcy) has been determined at 2.7 A resolution and reveals several novel features of the poxvirus capping enzyme. The structure shows for the first time the critical role played by the proteolytically sensitive N-terminus of the MT domain in binding the methyl donor and in catalysis. In addition, the poxvirus enzyme has a completely unique mode of binding of the adenosine moiety of AdoHcy, a feature that could be exploited for design of specific anti-poxviral compounds. The structure of the poxvirus-specific D12 subunit suggests that it was originally an RNA cap 2'O-MT that has evolved to a catalytically inactive form that has been retained for D1 stabilisation and MT activity enhancement through an allosteric mechanism.
authors.affiliation: Grenoble Outstation, European Molecular Biology Laboratory, Grenoble, France.
authors.forename: Marcos
authors.initials: M
authors.lastname: De la Peña
authors.forename: Otto J P
authors.initials: OJ
authors.lastname: Kyrieleis
authors.forename: Stephen
authors.initials: S
authors.lastname: Cusack
mesh_terms: D000495:Allosteric Site; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008780:Methyltransferases / Q000737:chemistry* / Q000502:physiology*; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012315:RNA Caps; D012435:S-Adenosylhomocysteine / Q000737:chemistry*; D014616:Vaccinia virus / Q000201:enzymology* / Q000235:genetics*
chemical_list: D012315:RNA Caps; D012435:S-Adenosylhomocysteine; D008780:Methyltransferases; C055097:mRNA (guanine(N7))-methyltransferase