BB lecture 11-14 translation detail

BB lecture 11-14 translation detail - Chapter 17...

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Unformatted text preview: Chapter 17 (pp.320-327) Protein synthesis II - Translation Learning objectives • Know where translation takes place • Know the role of aminoacyl-tRNA synthetase • Explain the process of how mRNA codons are translated into polypeptides • Learn how a protein may be “targeted” to the ER for development as a membrane or secreted protein • Know the functions of the different RNA types • Some additional terms to know include….codon & anticodon, codon wobble, P site, A site, E site, translation initiation complex, polysomes (polyribosomes), peptide bond formation, ribozyme, aminoacyl tRNA (aka “activated” tRNA)… Translation overview … TRANSCRIPTION TRANSLATION DNA mRNA Ribosome Polypeptide Polypeptide Amino acids tRNA with amino acid attached Ribosome tRNA Anticodon mRNA T r p Phe Gly A G C A A A C C G U G G U U U G G C Codons 5 ′ 3 ′ • Accurate translation requires two steps: – First step: a correct match between a t-RNA and an amino acid, done by the enzyme aminoacyl-tRNA synthetase – Second step: a correct match between the tRNA anticodon and an mRNA codon First: The structure of transfer RNA (tRNA) 3 ′ A C C A C G C U U A A G A C A C C U G C * G U G U C U GA G G U A A A G U C A G A C C C G A G A G G G G A C U C A U U U A G G C G 5 ′ Amino acid attachment site Hydrogen bonds Anticodon Two-dimensional structure . The four base-paired regions and three loops are characteristic of all tRNAs, as is the base sequence of the amino acid attachment site at the 3 ′ end. The anticodon triplet is unique to each tRNA type. (a) * * * * * * * * * * * • A tRNA molecule consists of a single RNA strand that is only about 80 nucleotides long Figure 17.14 Amino acid attachment site Hydrogen bonds Anticodon Anticodon (b) Three-dimensional structure A A G 5 ′ 3 ′ 3 ′ 5 ′ Symbol used in text (c) How does an amino acid get attached? Figure 17.15 An aminoacyl-tRNA synthetase joins a specific amino acid to a tRNA Amino acid ATP Adenosine Pyrophosphate Adenosine Adenosine Phosphates tRNA P P P P P P i P i P i P AMP Aminoacyl tRNA (an “activated amino acid”) Appropriate tRNA covalently bonds to amino Acid, displacing AMP. Active site binds the amino acid and ATP. 1 3 Activated amino acid is released by the enzyme. 4 Aminoacyl-tRNA synthetase (enzyme) ATP loses two Phosphate groups and joins amino acid as AMP. 2 • Accurate translation requires two steps: – First step: a correct match between a tRNA and an amino acid, done by the enzyme aminoacyl-tRNA synthetase – Second step: a correct match between the tRNA anticodon and an mRNA codon What is “wobble”? • Wobble refers to the relaxing of base-pair rules…but Figure 17.5 The dictionary of the genetic code Second mRNA base U C A G U C A G UUU UUC UUA UUG CUU CUC CUA CUG AUU AUC AUA AUG GUU GUC GUA GUG Met or start Phe Leu Leu lle Val UCU UCC UCA UCG CCU CCC CCA CCG ACU ACC ACA ACG GCU GCC GCA GCG Ser Pro Thr Ala UAU UAC UGU UGC Tyr Cys CAU CAC CAA CAG CGU CGC CGA...
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This note was uploaded on 10/06/2010 for the course BIO 311C taught by Professor Satasivian during the Fall '08 term at University of Texas at Austin.

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BB lecture 11-14 translation detail - Chapter 17...

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