LM6-3 - Translationandposttranslational processes...

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Translation and post-translational  processes • The ribosome • tRNAs – molecular translators • Initiation, elongation and termination of  translation • Polypeptide folding • Secretion of newly formed polypeptides • Synthesis/inhibitors of cell structure production:  cell wall 1
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The Bacterial ribosome (Fig. 12.35) Large subunit has 2 rRNAs (5S and 23S) + 34 proteins Small subunit has 1 rRNA (16S) + 21 proteins mRNAs lie between and contact both subunits Overall prokaryotic ribosome is 70S 2
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tRNAs (Fig. 12.33) 3 • Information stored in a  nucleotide sequence is  translated into information  in a polypeptide (AA  sequence) by tRNAs  • The various regions/loops  have functions: the  anticodon loop is  complementary to codons in  mRNA; the 3’A is attached to  the correct AA; other loops  interact with ribosomal  proteins
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More about tRNAs (Fig. 12.34) 4 • Aminoacyl-tRNA synthetases  charge tRNAs with correct amino  acids (i.e., the AA is covalently  attached) using energy from ATP • A high energy ester bond is  formed during the attachment of  the AA to last“A” at 3’ end of  tRNA, the hydrolysis of which  provides energy for formation of  peptide bond by ribosome •  Proofreading occurs – if a  mistake is made in charging the  tRNA, the bond is hydrolyzed and  the AA released
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The genetic code (Table 12.2, Fig. 12.31) • 64 potential codons exit, 3 are used as stop codons (there are  no tRNAs with the complementary anticodons; in some  species stop codons are used for rare amino acids)
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This note was uploaded on 03/31/2010 for the course MCB 3020 taught by Professor Ogden during the Spring '08 term at University of Florida.

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LM6-3 - Translationandposttranslational processes...

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