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The variable loop or V loop sits between the anticodon loop and the ΨU loop and, as its name implies, varies in size from 3 to 21 bases. In some tRNAs, the "loop" is long enough to form a rigid stem, the variable arm. [14] tRNAs with a V loop more than 10 bases long is classified as "class II" and the rest is called "class I". [15]
The T-arm or T-loop is a specialized region on the tRNA molecule which acts as a special recognition site for the ribosome to form a tRNA-ribosome complex during protein biosynthesis or translation (biology). The T-arm has two components to it; the T-stem and the T-loop.
The third arm, known as the "variable arm", has a stem with optional loop. [2] One end of the chains (with a double stranded structure in which the 5' and 3' ends are adjacent to each other), the amino acids acceptor stem, usually attaches to amino acids and such reactions are often catalyzed by a specific enzymes, aminoacyl tRNA synthetase. [3]
The stem-loop structure (also often referred to as an "hairpin"), in which a base-paired helix ends in a short unpaired loop, is extremely common and is a building block for larger structural motifs such as cloverleaf structures, which are four-helix junctions such as those found in transfer RNA. Internal loops (a short series of unpaired bases ...
In 1965, Holley et al. purified and sequenced the first tRNA molecule, initially proposing that it adopted a cloverleaf structure, based largely on the ability of certain regions of the molecule to form stem loop structures. [60] The isolation of tRNA proved to be the first major windfall in RNA structural biology. In 1971, Kim et al. achieved ...
Both tyrosyl-tRNA synthetases and tryptophanyl-tRNA synthetases belong to Class I of the aminoacyl-tRNA synthetases, both are dimers and both have a class II mode of tRNA recognition, i.e. they interact with their cognate tRNAs from the variable loop and major groove side of the acceptor stem.
It is composed of the two D stems and the D loop. The D loop contains the base dihydrouridine, for which the arm is named. [1] The D loop's main function is that of recognition. It is widely believed that it acts as a recognition site for aminoacyl-tRNA synthetase, an enzyme involved in the aminoacylation of the tRNA molecule.
The T-loop sequence is conserved across oomycetes and jakobid, with only few deviations (e.g., Saprolegnia ferax). Finally, instead of the tRNA-like D-stem with a shortened three-nucleotide D-loop characteristic for bacterial tmRNAs, mitochondrial counterparts have a highly variable 5 to 14-nt long loop.