A transfer RNA (abbreviated tRNA) is the physical link between the nucleotide sequence of nucleic acids, DNA and RNA, and the amino acid sequence of proteins. It makes this connection, by having at one end a three-nucleotide sequence, an anticodon, and at its other end the amino acid specified by that anticodon. For each of the 61 amino acid specifying codons in the genetic code, there is a transfer RNA with the corresponding anticodon. When the anticodon on the transfer RNA is matched to the next codon on the messenger RNA by the ribosome, then the ribosome attaches the growing protein to the amino acid the tRNA carries, extending the protein by one amino acid.
There are 61 aminoacyl-tRNA synthetases, one for each codon, and thus one for each distinct tRNA. Each aminoacyl-tRNA synthetases recognizes one anticodon, and attaches the correct amino acid specified by that anticodon to the tRNA containing it, in a process called "charging". Since there are 61 amino acid specifying codons, but only 20 amino acids used to make proteins, most amino acids have more than one transfer RNA.
The actual, physical point at which the connection is made between the genetic code, and a specific amino acid, is when the aminoacyl-tRNA synthetase charges the transfer RNA. Thus this is the critical step in the translation of the information stored in base sequence in DNA into a protein. Aminoacyl-tRNA synthetase is highly accurate, correctly charging 9,999 out of 10,000 times.[1]
Transfer RNA was at first called soluble RNA, sRNA, but once its biological roll was recognized the name was changed.[2]
- ^ Watson, James; Hopkins, Nancy; Roberts, Jeffrey; Steitz, Joan; Weiner, Alan (1987). Molecular Biology of the Gene (fourth ed.). Menlo Park: Benjamin/Cummings. p. 391. ISBN 0805396144.
- ^ Plescia, O J; Palczuk, N C; Cora-Figueroa, E; Mukherjee, A; Braun, W (October 1965). "Production of antibodies to soluble RNA (sRNA)". Proc Natl Acad Sci. 54 (4): 1281–1285. Retrieved 23 November 2014.