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Unformatted text preview: 1 DNA RNA Protein Replication Transcription Translation Lecture 50: Translation II (protein synthesis) Today’s lecture: Text pp. 1044-1058, 1101-1103 Preprinted lecture notes 86-96 Download from http://www.mbi.ufl.edu/facilities/msg/bch4024-notes.html Assembling the components Regulating translation Looking at large assemblies 1) mRNA is translated 5’ Æ 3’ 2) Polypeptide chain synthesis is amino (NH 3 + ) Æ carboxy (COO- ) 3) Three phases of the “ribosome cycle” a) Initiation: bind initiator tRNA……“AUG” b) Elongation: bind aa tRNAs and form peptide bonds c) Termination Some general features of protein synthesis 2 Protein synthesis requires energy 1) From ATP 1) Charging aatRNA (requires two ATPs since ATP Æ AMP) 2) Eukaryotic initiation 2) From GTP 1) For binding tRNA to ribosome 1) At initiation 2) During elongation 2) For translocation of peptidyl tRNA and growing protein chain (N-1 residues) 3) For termination (last residue) Estimated total (prokaryotes): 4 N ATP/GTP for a protein with N residues IF1 – promotes mRNA binding IF2 – initiator tRNA binding; binds GTP IF3 – Anti-association activity; promotes accurate start & mRNA binding Initiator tRNA binds at P site on 30S Shine-Dalgarno sequences position initiation codon in vicinity of decoding site, P site Chain initiation IF ≡ Initiation Factor protein Ribosome is “opened up” to allow positioning of mRNA strand A ≡ aminoacyl site P ≡ peptidyl site E ≡ exit site 3...
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- Fall '08
- Biochemistry, Protein biosynthesis, aatRNA, Initiation Factor protein