The D arm is a feature in the

tertiary structure Protein tertiary structure is the three dimensional shape of a protein. The tertiary structure will have a single polypeptide chain "backbone" with one or more protein secondary structures, the protein domains. Amino acid side chains may i ...

of transfer RNA (tRNA). It is composed of the two D stems and the D loop. The D loop contains the base

dihydrouridine Dihydrouridine (abbreviated as D, DHU, or UH2) is a pyrimidine nucleoside which is the result of adding two hydrogen atoms to a uridine, making it a fully saturated pyrimidine ring with no remaining double bonds. D is found in tRNA and rRNA molec ...

, for which the arm is named. 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 aminoacyl-tRNA synthetase (aaRS or ARS), also called tRNA-ligase, is an enzyme that attaches the appropriate amino acid onto its corresponding tRNA. It does so by catalyzing the transesterification of a specific cognate amino acid or its p ...

, an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

involved in the

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 ...

of the tRNA molecule. The D stem is also believed to have a recognition role although this has yet to be verified. It is a highly variable region and is notable for its unusual conformation due to the over-crowding on one of the

guanosine Guanosine (symbol G or Guo) is a purine nucleoside comprising guanine attached to a ribose ( ribofuranose) ring via a β-N9- glycosidic bond. Guanosine can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophosphate ...

residues. It appears to play a large role in the stabilization of the tRNA's tertiary structure.

References

{{DEFAULTSORT:D Arm RNA