Abstract
The 5' end of tobacco mosaic virus (TMV) genomic RNA is capped with 7-methylguanosine. A virus-coded polypeptide with guanylyltransferase activity has been investigated. This enzyme is responsible for forming the 5'----5' linkage of guanosine 5'-monophosphate to the 5'-diphosphate of an acceptor RNA, thereby forming the cap. A critical step in the mechanism for cap formation in the eukaryotic nucleus is for guanylyltransferase to bind covalently to guanosine 5'-monophosphate with the hydrolysis of pyrophosphate when guanosine 5'-triphosphate is the substrate. The TMV 126-kilodalton protein, which is most probably a component of the TMV replicase, was found to have this activity. The mechanism of this reaction has been characterized biochemically.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Binding, Competitive
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Cations, Divalent
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Cell Fractionation
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Guanine Nucleotides / metabolism
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Guanine Nucleotides / pharmacology
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Guanosine / analogs & derivatives
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Guanosine / metabolism
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Guanosine Monophosphate / metabolism
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Guanosine Triphosphate / metabolism
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Immunosorbent Techniques
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Molecular Weight
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Nicotiana / microbiology
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Nucleotides / metabolism
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Nucleotidyltransferases / genetics
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Nucleotidyltransferases / metabolism*
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Phosphates / metabolism
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Phosphates / pharmacology
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Plants, Toxic
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RNA Caps*
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RNA, Viral / metabolism*
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Substrate Specificity
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Tobacco Mosaic Virus / enzymology
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Tobacco Mosaic Virus / genetics*
Substances
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Cations, Divalent
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Guanine Nucleotides
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Nucleotides
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Phosphates
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RNA Caps
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RNA, Viral
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Guanosine
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7-methylguanosine
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Guanosine Monophosphate
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Guanosine Triphosphate
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Nucleotidyltransferases
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guanylyltransferase