Transfer RNA (tRNA): Difference between revisions
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'''tRNA''' or transfer RNA plays a key role in translation, the process of synthesizing proteins from amino acids in a sequence specified by information contained in messenger RNA. During this process, triplets of nucleotides (codons) of the messenger RNA are translated according to the genetic code into one of the 20 amino acids. tRNAs serve as the dictionary in this translation process. [[Image:Translation RNA amino acid.png|right|thumb|350px|Translation of RNA sequence into protein sequence]] They contain a specific triplet nucleotide sequence, the anticodon, and they get attached to a specific (cognate) amino acid. During protein synthesis by ribosomes, tRNAs deliver the correct amino acids through interactions of their anticodon region with the complementary codons on the messenger RNA. Apart from their distinct anticodon regions, different tRNAs have very similar structures, allowing them to all fit into the tRNA-binding sites on the ribosome. | '''tRNA''' or transfer RNA plays a key role in translation, the process of synthesizing proteins from amino acids in a sequence specified by information contained in messenger RNA. During this process, triplets of nucleotides (codons) of the messenger RNA are translated according to the genetic code into one of the 20 amino acids. tRNAs serve as the dictionary in this translation process. [[Image:Translation RNA amino acid.png|right|thumb|350px|Translation of RNA sequence into protein sequence]] They contain a specific triplet nucleotide sequence, the anticodon, and they get attached to a specific (cognate) amino acid. During protein synthesis by ribosomes, tRNAs deliver the correct amino acids through interactions of their anticodon region with the complementary codons on the messenger RNA. Apart from their distinct anticodon regions, different tRNAs have very similar structures, allowing them to all fit into the tRNA-binding sites on the ribosome. | ||
<StructureSection load='' size='350' side='right' scene='43/433638/Fullview_cartoon/8' caption='Phenylalanine-tRNA from yeast (PDB code [[1ehz]])'> | <StructureSection load='' size='350' side='right' scene='43/433638/Fullview_cartoon/8' caption='Phenylalanine-tRNA from yeast (PDB code [[1ehz]])'> | ||
==Structure== | ==Structure== | ||
tRNA is a stable, folded type of RNA present in all living cells. The secondary structure of most tRNA<ref>PMID:4601792</ref><ref>PMID:4612535</ref> is composed of four helical stems (shown in cyan, blue, red and yellow) arranged in a cloverleaf structure and an central four-way junction. <scene name='43/433638/Wireframe/1'>In three dimensions</scene>, tRNA adopts an "L" shape, with the <jmol> | [[Image:TRNA phe yeast.png|left|thumb|Standard 2D cloverleaf structure of tRNA. The shown example is phenylalanine-specific tRNA from yeast]]tRNA is a stable, folded type of RNA present in all living cells. The secondary structure of most tRNA<ref>PMID:4601792</ref><ref>PMID:4612535</ref> is composed of four helical stems (shown in cyan, blue, red and yellow) arranged in a cloverleaf structure and an central four-way junction. <scene name='43/433638/Wireframe/1'>In three dimensions</scene>, tRNA adopts an "L" shape, with the <jmol> | ||
<jmolLink> | <jmolLink> | ||
<script> select 73-76; spacefill on; delay 0.5; spacefill off; | <script> select 73-76; spacefill on; delay 0.5; spacefill off; | ||
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The anticodon loop of the tRNA quite often contains hypermodified bases, the function of which is to stabilize the codon-anticodon interaction within the ribosome. The nature and position of nucleotide modifications is both specific of the organism and the tRNA type. Common modified nucleotides include: | The anticodon loop of the tRNA quite often contains hypermodified bases, the function of which is to stabilize the codon-anticodon interaction within the ribosome. The nature and position of nucleotide modifications is both specific of the organism and the tRNA type. Common modified nucleotides include: | ||
* 5-methyluridine (ribothymidine) at position 54 | * 5-methyluridine (ribothymidine) at position 54 | ||
* <scene name='43/433638/Pseudouridine/2'>pseudouridine at position 55</scene> | * <scene name='43/433638/Pseudouridine/2'>pseudouridine at position 55</scene> (note the <jmol><jmolLink> | ||
<script> select 55 and (*.C5, *.C1*);wireframe 0.3; color bonds cyan; delay 1.2;wireframe 0.14;color bonds none; | |||
</script> | |||
<text>carbon-carbon bond</text> | |||
</jmolLink> | |||
</jmol> connecting sugar and base) | |||
* dihydrouridine(s) in the D-loop | * dihydrouridine(s) in the D-loop | ||
* 7-methylguanosine at position 46 | * 7-methylguanosine at position 46 | ||