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Pyrrolysine is an α-amino acid that is used in the biosynthesis of proteins in some methanogenic archaea and bacteria; it is not present in humans. It contains an α-amino group, a carboxylic acid group. Its pyrroline side-chain is similar to that of lysine in being basic and positively charged at neutral pH.
A transfer RNA is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length, that serves as the physical link between the mRNA and the amino acid sequence of proteins. tRNA does this by carrying an amino acid to the protein synthetic machinery of a cell (ribosome) as directed by the complementary recognition of a 3-nucleotide sequence (codon) in a messenger RNA (mRNA) by a 3-nucleotide sequence (anticodon) of the tRNA. As such, tRNAs are a necessary component of translation, the biological synthesis of new proteins in accordance with the genetic code.
An aminoacyl-tRNA synthetase, also called tRNA-ligase, is an enzyme that attaches the appropriate amino acid onto its tRNA. It does so by catalyzing the esterification of a specific cognate amino acid or its precursor to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA. In humans, the 20 different types of aa-tRNA are made by the 20 different aminoacyl-tRNA synthetases, one for each amino acid of the genetic code.
Aminoacyl-tRNA is tRNA to which its cognate amino acid is chemically bonded (charged). The aa-tRNA, along with particular elongation factors, deliver the amino acid to the ribosome for incorporation into the polypeptide chain that is being produced during translation.
In enzymology, an arginine-tRNA ligase is an enzyme that catalyzes the chemical reaction
Aspartate---tRNAAsn ligase is an enzyme with systematic name L-aspartate:tRNAAsx ligase (AMP-forming). This enzyme catalyses the following chemical reaction
In enzymology, a phenylalanine-tRNA ligase is an enzyme that catalyzes the chemical reaction
In enzymology, a threonine-tRNA ligase is an enzyme that catalyzes the chemical reaction
Tyrosine—tRNA ligase, also known as tyrosyl-tRNA synthetase, is an enzyme that catalyzes the chemical reaction
Tyrosyl-tRNA synthetase, cytoplasmic, also known as Tyrosine-tRNA ligase, is an enzyme that in humans is encoded by the YARS gene.
Bifunctional aminoacyl-tRNA synthetase is an enzyme that in humans is encoded by the EPRS gene.
Isoleucyl-tRNA synthetase, cytoplasmic is an enzyme that in humans is encoded by the IARS gene.
Asparaginyl-tRNA synthetase, cytoplasmic is an enzyme that in humans is encoded by the NARS gene.
An expanded genetic code is an artificially modified genetic code in which one or more specific codons have been re-allocated to encode an amino acid that is not among the 22 common naturally-encoded proteinogenic amino acids.
Probable histidyl-tRNA synthetase, mitochondrial is an enzyme that in humans is encoded by the HARS2 gene.
Amino acid activation refers to the attachment of an amino acid to its Transfer RNA (tRNA).
The aminoacyl-tRNA synthetases catalyse the attachment of an amino acid to its cognate transfer RNA molecule in a highly specific two-step reaction. These proteins differ widely in size and oligomeric state, and have limited sequence homology. The 20 aminoacyl-tRNA synthetases are divided into two classes, I and II. Class I aminoacyl-tRNA synthetases contain a characteristic Rossmann fold catalytic domain and are mostly monomeric. Class II aminoacyl-tRNA synthetases share an anti-parallel beta-sheet fold flanked by alpha-helices, and are mostly dimeric or multimeric, containing at least three conserved regions. However, tRNA binding involves an alpha-helical structure that is conserved between class I and class II synthetases. In reactions catalysed by the class I aminoacyl-tRNA synthetases, the aminoacyl group is coupled to the 2'-hydroxyl of the tRNA, while, in class II reactions, the 3'-hydroxyl site is preferred. The synthetases specific for arginine, cysteine, glutamic acid, glutamine, isoleucine, leucine, methionine, tyrosine, tryptophan and valine belong to class I synthetases; these synthetases are further divided into three subclasses, a, b and c, according to sequence homology. The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, lysine, phenylalanine, proline, serine, and threonine belong to class-II synthetases.
The B3/B4 domain, is found in tRNA synthetase beta subunits, as well as in some non-tRNA synthetase proteins.
In molecular biology, YqeY is a type of protein domain of unknown function. It is thought to have a role in protein synthesis, facilitating the production of charged transfer RNA used in the process of translating mRNA into protein. It is present as a domain of glutaminyl-tRNA synthetase (GlnRS) in almost all eukaryotes.
The aspS RNA motif is a conserved RNA structure that was discovered by bioinformatics. aspS motifs are found in a specific lineage of Actinobacteria.
References
- ↑ Delarue M, Moras D, Poch O, Eriani G, Gangloff J (1990). "Partition of tRNA synthetases into two classes based on mutually exclusive sets of sequence motifs". Nature. 347 (6289): 203–206. Bibcode:1990Natur.347..203E. doi:10.1038/347203a0. PMID 2203971. S2CID 4324290.
- ↑ Moras D, Konno M, Shimada A, Nureki O, Tateno M, Yokoyama S, Sugiura I, Ugaji-Yoshikawa Y, Kuwabara S, Lorber B, Giege R (2000). "The 2.0 A crystal structure of Thermus thermophilus methionyl-tRNA synthetase reveals two RNA-binding modules". Structure. 8 (2): 197–208. doi:10.1016/S0969-2126(00)00095-2. PMID 10673435.
- ↑ Perona JJ, Steitz TA, Rould MA (1993). "Structural basis for transfer RNA aminoacylation by Escherichia coli glutaminyl-tRNA synthetase". Biochemistry. 32 (34): 8758–8771. doi:10.1021/bi00085a006. PMID 8364025.
- ↑ Delarue M, Moras D (1993). "The aminoacyl-tRNA synthetase family: modules at work". BioEssays. 15 (10): 675–687. doi:10.1002/bies.950151007. PMID 8274143. S2CID 35612984.
- ↑ Schimmel P (1991). "Classes of aminoacyl-tRNA synthetases and the establishment of the genetic code". Trends Biochem. Sci. 16 (1): 1–3. doi:10.1016/0968-0004(91)90002-D. PMID 2053131.
- ↑ Cusack S, Leberman R, Hartlein M (1991). "Sequence, structural and evolutionary relationships between class 2 aminoacyl-tRNA synthetases". Nucleic Acids Res. 19 (13): 3489–3498. doi:10.1093/nar/19.13.3489. PMC 328370 . PMID 1852601.
- ↑ Bairoch A (2004). "List of aminoacyl-tRNA synthetases".Cite journal requires
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