Lecture 6 Protein Synthesis

Lecture 6 Protein Synthesis - Chapter30 ProteinSynthesis...

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Chapter 30 Protein Synthesis  
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Protein synthesis Translation of nucleotide sequences into amino acid sequences Ingredients - mRNA: codons - aminoacyl-tRNA (amino acid + tRNA): binds codon & brings amino acid - ribosome: factory for the manufacture of polypeptides Reaction steps: initiation ~ elongation ~ termination Proteins are synthesized by the successive addition of amino acids to the  carboxyl terminus Amino terminal Carboxyl terminal error frequency   10 -4 [Polypeptide-chain growth]
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I.  Ingredients A. mRNAs  (m=messenger):  three  base codons B. tRNAs  (t=transfer) Single  chain RNA containing 73~93 ribonucleotides with many unusual  (modified) bases (methylation, deamination, etc.) Serves as the adaptor molecule that binds to a specific codon in mRNA and  brings an amino acid for incorporation into the polypeptide chain There are many kinds of tRNAs Three nucleotides  complementary to mRNA Base pairing determines  specificity tRNA mRNA G
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tRNA structure Different tRNA molecules have a similar overall structure:    cloverleaf;  L-shaped About half the nucleotides are base-paired to form double helices (four  helical regions:  A DNA-form Anticodon  is in a loop near the  center  of the sequence Amino acid is attached to the  adenosine  residue located at the end of  the 3’ CCA    Anticodon
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(i) Amino acid + ATP     Aminoacyl-AMP +PPi + tRNA + AMP Formation of aminoacyl-tRNA Specific amino acid is attached to the 2’ or 3’  hydroxyl group of the adenosine at the 3’ end of  the corresponding tRNA Aminoacyl-tRNA synthetase  specific  to each  amino acid forms “charged” tRNAs (ii)
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Aminoacyl-tRNA synthetases At least  one aminoacyl-tRNA synthetase exists for each amino acid Each aminoacyl-tRNA synthetase is  highly specific  for a given amino acid Activation site: highly discriminating Editing site: proofreading - wrong amino acid is removed by  hydrolysis tRNA aminoacyl-tRNA sysnthetase (threonyl-tRNA synthetase) (unique to tRNA Thr   synthetase) NH 3 OH
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This note was uploaded on 01/16/2012 for the course BIOLCHEM 415 taught by Professor Michaeluhler during the Fall '06 term at University of Michigan.

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Lecture 6 Protein Synthesis - Chapter30 ProteinSynthesis...

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