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From Proteopedia
VACCINIA METHYLTRANSFERASE VP39 MUTANT (EC: 2.7.7.19)
Structural highlights
Function[MCE_VACCW] Displays methyltransferase, positive regulation of the poly(A) polymerase and transcription elongation activities. Involved in the modification of both mRNA ends and in intermediate and late gene positive transcription elongation. At the mRNAs 5' end, methylates the ribose 2' OH group of the first transcribed nucleotide, thereby producing a 2'-O-methylpurine cap. At the 3' end, functions as a processivity factor which stimulates the activity of the viral poly(A) polymerase VP55 that creates mRNA's poly(A) tail. In the presence of VP39, VP55 does not dissociate from the RNA allowing tail elongation to around 250 adenylates.[1] [2] [3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedWe have determined, by high resolution x-ray analysis, 10 structures comprising the mRNA cap-specific methyltransferase VP39 or specific mutants thereof in the presence of methylated nucleobase analogs (N1-methyladenine, N3-methyladenine, N1-methylcytosine, N3-methylcytosine) and their unmethylated counterparts, or nucleoside N7-methylguanosine. Together with solution affinity studies and previous crystallographic data for N7-methylguanosine and its phosphorylated derivatives, these data demonstrate that only methylated, positively charged bases are bound, indicating that their enhanced stacking with two aromatic side chains of VP39 (Tyr 22 and Phe 180) plays a dominant role in cap recognition. Four key features characterize this stacking interaction: (i) near perfect parallel alignment between the sandwiched methylated bases and aromatic side chains, (ii) substantial areas of overlap in the two-stacked rings, (iii) a 3.4-A interplanar spacing within the overlapping region, and (iv) positive charge in the heterocyclic nucleobase. mRNA cap recognition: dominant role of enhanced stacking interactions between methylated bases and protein aromatic side chains.,Hu G, Gershon PD, Hodel AE, Quiocho FA Proc Natl Acad Sci U S A. 1999 Jun 22;96(13):7149-54. PMID:10377383[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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