The role of queuine in the aminoacylation of mammalian aspartate transfer RNAs.
Can a queuine-specific tRNA function normally without replacement of G by Q in its structure? To answer this, kinetics of aspartate queuine-containing tRNA (Q-tRNA) is compared with its queuine-deficient counterpart (G-tRNA). The results indicate that Asp Q-tRNA is a more effective substrate than the Asp G-tRNA. The Asp Q-tRNA exhibits a higher reaction velocity (Vmax greater than 30%) and a higher reaction rate (Km less than 55%) than its counterpart. The Asp tRNAs derived from human tumor lines and grown in athymic mice contain a full complement of queuine. This tumor tRNA exhibits aminoacylation kinetics similar to a normal liver tRNA. Reasons for observing the lack of a G-to-Q modification in cancer tRNAs by others are hypothesized. Two purified Asp isoacceptors from liver are compared for the aminoacylation reaction; small differences are noted in the Vmax, but none in the Km values.
D000818:Animals; D001226:Aspartate-tRNA Ligase / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D005260:Female; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008175:Lung Neoplasms / Q000032:analysis; D051379:Mice; D010051:Ovarian Neoplasms / Q000032:analysis; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*
D012346:RNA, Transfer, Amino Acyl; D006147:Guanine; C019549:queuine; D001226:Aspartate-tRNA Ligase