The T-arm or T-loop is a specialized region on the

tRNA Transfer ribonucleic acid (tRNA), formerly referred to as soluble ribonucleic acid (sRNA), is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes). In a cell, it provides the physical link between the gene ...

molecule which acts as a special recognition site for the

ribosome Ribosomes () are molecular machine, macromolecular machines, found within all cell (biology), cells, that perform Translation (biology), biological protein synthesis (messenger RNA translation). Ribosomes link amino acids together in the order s ...

to form a tRNA-ribosome complex during

protein biosynthesis Protein biosynthesis, or protein synthesis, is a core biological process, occurring inside Cell (biology), cells, homeostasis, balancing the loss of cellular proteins (via Proteolysis, degradation or Protein targeting, export) through the produc ...

translation (biology) In biology, translation is the process in living Cell (biology), cells in which proteins are produced using RNA molecules as templates. The generated protein is a sequence of amino acids. This sequence is determined by the sequence of nucleotide ...

. The T-arm has two components to it; the T-stem and the T-loop. * The T-stem consists of a series of paired nucleotides, typically 5 pairs, but sometimes as few as 1 or as many as 6. * The T-loop is also often known as the TΨC arm due to the presence of ribothymidine (T/m5U), pseudouridine and

cytidine Cytidine (symbol C or Cyd) is a nucleoside molecule that is formed when cytosine is attached to a ribose ring (also known as a ribofuranose) via a β-N1-glycosidic bond. Cytidine is a component of RNA. It is a white water-soluble solid that is ...

residues. It folds into a unique structural element consisting of stacked bases in a U-turn, now termed the "T-loop motif". ** In archaea, the m5U is replaced with N1-methylpseudouridine (m1Ψ). The m5U/m1Ψ modification at position 54 is thought to increase structural stability. Organisms with T-loop lacking tRNA exhibit a much lower level of

aminoacylation Aminoacylation is the process of adding an aminoacyl group to a compound. See also * Acylation * tRNA aminoacylation * Transfer RNA-like structures References Organic reactions {{Reaction-stub ...

and

EF-Tu EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome. It is a G-protein, and facilitates the selection and binding of an aa-tRNA to t ...

-binding than in organisms which have the native tRNA. The T-loop motif has been identified as a ubiquitous structural element in a number of noncoding RNAs. At least one other instance of the T-loop, found in rRNA, also carries the m5U modification.

References

{{DEFAULTSORT:T Arm RNA Protein biosynthesis