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 allow a tRNA-ribosome complex to form during the process of protein biosynthesis.

The T-arm has two components to it; the T-stems and the T-loop.

• There are two T-stems of five base pairs each. T-stem 1 is from 49-53 and T-stem 2 is from 61-65.
• The T-loop is also often known as the TΨC arm due to the presence of thymidine, pseudouridine and cytidine residues. tRNA is the only RNA species that contains the nucleoside thymidine.

Organisms with T-loop lacking tRNA exhibit a much lower level of aminoacylation and EF-Tu-binding than in organisms which have the native tRNA.

In Mammalian DNA, telomeric repeat-binding factor 2 or TRF2 has been found to remodel linear telomeric DNA into large T-loops.

References

• Griffith Jack D. et al. Mammalian Telomeres End in Large Duplex Loop. 1999. Cell Press. 97;503-514