Transcription and Translation RNA
Transcription and Translation RNA
Transcription and Translation RNA
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How are amino acids attached to a t<strong>RNA</strong>?<br />
Each t<strong>RNA</strong><br />
can only<br />
carry one<br />
specific<br />
amino acid.<br />
5'<br />
3'<br />
Amino acyl<br />
t<strong>RNA</strong> synthetase<br />
5'<br />
Threonine<br />
AGU Threonine AMP + PPi<br />
AGU<br />
ATP<br />
A t<strong>RNA</strong> carrying an amino acid is said to be charged. But the amino acid that is<br />
attached to the t<strong>RNA</strong> is said to be activated. The enzyme that attaches the amino acid to the<br />
t<strong>RNA</strong> is called aminoacyl t<strong>RNA</strong> synthetase. Charging a t<strong>RNA</strong> consumes energy in the form<br />
of ATP. Energy from the ATP is conserved in bond between amino acid <strong>and</strong> t<strong>RNA</strong>.<br />
Charged t<strong>RNA</strong><br />
Amino acid are<br />
attached to the t<strong>RNA</strong><br />
through the terminal<br />
3' adenosine residue<br />
found in t<strong>RNA</strong>.<br />
D-loop<br />
D-Stem<br />
5' end<br />
Acceptor<br />
Stem<br />
CCA<br />
end<br />
Anticodon<br />
stem<br />
TΨC loop<br />
Threonine<br />
HO<br />
CH2<br />
H<br />
O<br />
NH 2<br />
C<br />
C<br />
O<br />
N<br />
N<br />
CH(CH3)OH<br />
O<br />
t<strong>RNA</strong><br />
N<br />
NH 2<br />
N<br />
Threonine<br />
Adenylate<br />
AGU<br />
Anticodon loop<br />
The last three nucleotides on the 3' end of a t<strong>RNA</strong> are cytidylate (C) cytidylate (C) <strong>and</strong><br />
adenylate (A). That is 5' CCA 3'. Amino acids are attached to the t<strong>RNA</strong> through the<br />
adenylate residue. They are attached through a carboxylic bond to the 2' or 3' carbon of the<br />
adenylate residue.<br />
Remember that bacteria have 30 to 40 different t<strong>RNA</strong>s <strong>and</strong> eukaryotes have about 50<br />
different t<strong>RNA</strong>s. There is one amino acid synthetase for each amino acid. That is, there are<br />
20 different aminoacyl t<strong>RNA</strong> synthetases. Each individual synthetase charges all of the<br />
t<strong>RNA</strong>s that encode one particular amino acid. That is; each synthetase is specific for one<br />
amino acid. For example, if an organism has three t<strong>RNA</strong> arg 's then the enzyme arginine<br />
aminoacyl t<strong>RNA</strong> synthetase will charge all of the three t<strong>RNA</strong>s. Some aminoacyl t<strong>RNA</strong><br />
synthetases recognize their particular t<strong>RNA</strong>s based upon the shape of the molecule while<br />
others seem to recognize the anticodon loop itself.<br />
page 5.18 Revised 8/24/98
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