tRNAmolekylet

tRNAmolekylet, commonly known as transfer RNA (tRNA), is a small RNA molecule that functions as an adaptor in protein synthesis. During translation, tRNA carries a specific amino acid to a ribosome and recognizes the corresponding codon in messenger RNA through its anticodon loop. The correct pairing ensures that the amino acid is added to the growing polypeptide in the sequence dictated by the mRNA.

Most tRNAs share a conserved cloverleaf secondary structure consisting of an acceptor (CCA) terminus, the D loop, the anticodon loop, the variable loop, and the TΨC loop. In three-dimensional structure, tRNA adopts an L-shaped fold that presents the anticodon for codon recognition on one end and the aminoacyl end on the other. tRNAs are aminoacylated by aminoacyl-tRNA synthetases, which couple a specific amino acid to the 3' end of the tRNA. This process is selective for both the amino acid and the tRNA identity elements. The CCA sequence at the 3' terminus is usually added post-transcriptionally by tRNA nucleotidyltransferase in most organisms.

tRNA genes are transcribed by RNA polymerase III in eukaryotes and in archaea and bacteria, with processing and maturation including trimming and modification to generate functional tRNAs. Modifications at numerous positions stabilize structure and influence decoding, including wobble rules that expand codon recognition. Organelles such as mitochondria carry their own tRNA genes, sometimes with atypical structures or truncated 3' ends. tRNAmolekylet-derived RNAs, such as tRNA fragments, are also studied for regulatory roles. Malfunction of tRNA charging or decoding can lead to cellular defects and disease.