| initiation tRNA | TRNA in prokaryotes containing a formyl-methionyl residue that initiates translation. Synonym: formyl-methionyl-tRNA, starter tRNA. (05 Mar 2000) |
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| peptide chain initiation | The process whereby the formation of a peptide chain is started. This process requires (1) the 30s subunit, (2) the mRNA coding for the polypeptide to be made, (3) met-trnai, (4) initiation factors, and (5) GTP. (12 Dec 1998) |
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| peptide initiation factors | Protein factors uniquely required during the initiation phase of protein synthesis. (12 Dec 1998) |
| initiation | 1. The first stage of tumour induction by a carcinogen; subtle alteration of cells by exposure to a carcinogenic agent so that they are likely to form a tumour upon subsequent exposure to a promoting agent (promotion). 2. Starting point of replication or translation in macromolecule biosynthesis. 3. Start of chemical or enzymatic reaction. (05 Mar 2000) |
| initiation codon | The codon 5' AUG in mRNA, at which polypeptide synthesis is started. It is recognised by formylmethionyl tRNA in bacteria and by methionyl tRNA in eukaryotes. (18 Nov 1997) |
| initiation complex | Complex between mRNA, 30S ribosomal subunit and formyl methionyl tRNA that requires GTP and initiation factors to function. (18 Nov 1997) |
| initiation factor | One of several soluble proteins involved in the initiation of protein or RNA synthesis. (05 Mar 2000) |
| initiation factors | The set of catalytic proteins required, in addition to mRNA and ribosomes, for protein synthesis to begin. In bacteria three distinct proteins have been identified: if 1 (8 kD), IF 2 (75 kD) and IF 3 (30 kD). at least 6-8 proteins have been identified in eukaryotes. IFs 1 and 2 enhance the binding of initiator tRNA to the initiation complex. (18 Nov 1997) |
| tumour initiation | <cell biology, oncology> First stage of tumour development. See: tumour progression. (18 Nov 1997) |
| alanine-trna ligase | <enzyme> An enzyme that activates alanine with its specific transfer RNA. Chemical name: L-Alanine:tRNA(Ala) ligase (AMP-forming) Registry number: EC 6.1.1.7 (12 Dec 1998) |
| aminoacid-tRNA ligases | Recommended name for aminoacyl-tRNA synthetases, e.g., tyrosine-tRNA ligase for tyrosyl-tRNA synthetase. (05 Mar 2000) |
| aminoacyl-tRNA | <molecular biology> The name of the complex created when a tRNA molecule is attached to its specific amino acid and ready to participate in protein synthesis. (13 Oct 1997) |
| amino acyl-tRNA ligases | <enzyme> Any of the group of ligases that catalyses the ATP-driven formation of a bond between an amino acid and a trna, activating the amino acids as a step in protein synthesis. Individual enzymes are highly specific for one amino acid and for any trna corresponding to that amino acid. Registry number: EC 6.1.1. (12 Dec 1998) |
| aminoacyl-tRNA synthetases | <enzyme> Enzymes catalyzing the formation of a specific aminoacyl-tRNA from an amino acid and adenosine 5'-triphosphate with the concomitant formation of adenosine 5'-monophosphate and pyrophosphate. Synonym: amino acid activating enzyme, aminoacyl-tRNA ligases. (05 Mar 2000) |
| arginine-trna ligase | <enzyme> An enzyme that activates arginine with its specific transfer RNA. Chemical name: L-Arginine:tRNA(Arg)ligase (AMP-forming) Registry number: EC 6.1.1.19 (12 Dec 1998) |
| aspartate-trna ligase | <enzyme> An enzyme that activates aspartic acid with its specific transfer RNA. Chemical name: L-Aspartate:tRNA-(Asp) ligase (AMP-forming) Registry number: EC 6.1.1.12 (12 Dec 1998) |