. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DHU TyC T\|/C \ <o I. CCA anticodon anticodon top half minihelix contains critical functional contacts for CCA-adding enzyme TyC CCA Figure 1. The top half of tRN A is an independent structural and functional domain, which may have evolved independently from the bottom half. Shown is the traditional cloverleaf diagram of tRNA structure (left); a diagram which illustrates the coaxial stack of the dihydrouracil (DHU) and anticodon stems (center); and a diagram which illustrates the top half minihelices which are good substr
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DHU TyC T\|/C \ <o I. CCA anticodon anticodon top half minihelix contains critical functional contacts for CCA-adding enzyme TyC CCA Figure 1. The top half of tRN A is an independent structural and functional domain, which may have evolved independently from the bottom half. Shown is the traditional cloverleaf diagram of tRNA structure (left); a diagram which illustrates the coaxial stack of the dihydrouracil (DHU) and anticodon stems (center); and a diagram which illustrates the top half minihelices which are good substrates for the CCA-adding enzyme (right) (19). anticodon stem-loop (Fig. 1). Based upon the widespread roles of top-half'tRNA-like structures in replication of con- temporary RNA genomes, we have suggested that the top- half domain had an independent and more ancient origin than the anticodon domain (2. 4). The separable interactions of the top half and anticodon domains with the 23S and 16S rRNAs, respectively, also led Noller to suggest that these domains of tRNA evolved independently (12). Schimmel et nl. (13) reached similar conclusions by a very different route, based on the modular interaction of tRNA synthetases with the top and bottom halves of tRNA. The top-half domain, sometimes referred to as a tRNA "minihelix," has been shown to provide the determinants necessary for spe- cific charging by aminoacyl tRNA synthetases (14, 15); for interaction with elongation factor Tu (16); for 5' processing by RNase P (17); and for distinguishing elongator from initiator tRNA (18). However, it had not been established whether top-half minihelices could function as substrates for the CCA-adding enzyme. We have recently carried out two sorts of experiments designed to ask whether the top-half domain of tRNA has the necessary determinants for efficient CCA addition, and whether critical contacts between the tRNA and the CCA- adding enzyme lie within this domain. By analyzing CC
Size: 1384px × 1806px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
