Histidine tRNA Guanylyltransferase from Saccharomyces cereuisiae
نویسنده
چکیده
Yeast histidine tRNA guanylyltransferase (TGT) catalyzes in the presence of ATP the addition of GTP to the 5‘ end of eukaryotic cytoplasmic tRNAHi” species. A study of the enzyme mechanism with purified protein showed that during the first step ATP is cleaved to AMP and PPi creating adenylylated TGT. In a second step the activated enzyme forms a stable complex with its cognate tRNA substrate. The 5”phosphate of the tRNA is adenylylated by nucleotide transfer from the adenylylated guanylyltransferase to form A(5’)pp(5’)N at the 5’-end of the tRNA. Finally, the 3“hydroxyl of GTP adds to th e activated 5‘ terminus of the tRNA with the release of AMP. This mechanism of tRNAHi” guanylyltransferase is very similar to that of RNA ligases. dATP can substitute for ATP in this reaction. Since among several guanosine compounds active in this reaction GTP is most efficiently added we believe that it is the natural substrate of TGT.
منابع مشابه
tRNAHis-guanylyltransferase establishes tRNAHis identity
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