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-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 ribothymidine (T/m5U), pseudouridine and cytidine residues. It folds into a unique structural element consisting of 5 stacked bases in a U-turn, now termed the "T-loop motif".[1]
- In archaea, the m5U is replaced with N1-methylpseudouridine (m1Ψ). The m5U/m1Ψ modification at position 54 is thought to increase structural stability.[2]
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.
The T-loop motif has been identified as a ubiquitous structural element in a number of noncoding RNAs.[1] At least one other instance of the T-loop, found in rRNA, also carries the m5U modifictaion.[3]
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References
- ^ a b Chan, CW; Chetnani, B; Mondragón, A (September 2013). "Structure and function of the T-loop structural motif in noncoding RNAs". Wiley Interdisciplinary Reviews. RNA. 4 (5): 507–22. doi:10.1002/wrna.1175. PMC 3748142. PMID 23754657.
- ^ Wurm JP, Griese M, Bahr U, Held M, Heckel A, Karas M, et al. (March 2012). "Identification of the enzyme responsible for N1-methylation of pseudouridine 54 in archaeal tRNAs". RNA. 18 (3): 412–420. doi:10.1261/rna.028498.111. PMC 3285930. PMID 22274954.
In contrast, in most archaea this position is occupied by another hypermodified nucleotide: the isosteric N1-methylated pseudouridine
- ^ Powell, CA; Minczuk, M (April 2020). "TRMT2B is responsible for both tRNA and rRNA m(5)U-methylation in human mitochondria". RNA Biology. 17 (4): 451–462. doi:10.1080/15476286.2020.1712544. PMC 7237155. PMID 31948311.