Dunigan D D, Zaitlin M
Department of Plant Pathology, Cornell University, Ithaca, New York 14853.
J Biol Chem. 1990 May 15;265(14):7779-86.
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.
烟草花叶病毒（TMV）基因组RNA的5'端带有7-甲基鸟苷帽。一种具有鸟苷酸转移酶活性的病毒编码多肽已得到研究。这种酶负责形成鸟苷5'-单磷酸与受体RNA的5'-二磷酸之间的5'----5'连接，从而形成帽结构。真核细胞核中帽结构形成机制的关键步骤是，当鸟苷5'-三磷酸作为底物时，鸟苷酸转移酶与鸟苷5'-单磷酸共价结合并伴有焦磷酸水解。发现TMV 126千道尔顿蛋白很可能是TMV复制酶的一个组分，它具有这种活性。该反应机制已通过生化方法得以表征。
