Chapter30 - Biochemistry I Translation Protein Synthesis in...

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Biochemistry I Translation Protein Synthesis in Prokaryotes Dr. Ray Dr. Ray Chapter 30 What are the 5 phases of translation? 1. 2. 3. 4. 5.
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Overview of Protein Synthesis http://tidepool.st.usm.edu/crswr/110proteinsynthesis.html See movie at this site (if you have Apple Quicktime plugin) 1.During a preparatory step, activation, tRNA molecules are linked to their respective amino acids, forming complexes called aminoacyl-tRNAs. This step occurs in the cytoplasm and relies on enzymes called aminoacyl-tRNA synthetases. 1. Initiation is the first phase of protein translation. During initiation: the leading codon (AUG) of the messenger RNA molecule associates with the small subunit of a ribosome the AUG codon associates with the UAC anticodon of an aminoacyl-tRNA which bears the amino acid, methionine the small ribosomal subunit associates with a large ribosomal subunit in such a way as to position the attached tRNA at the P site (peptidyl binding site) The end result of this phase is the formation of an initiation complex. 3. During the second phase of protein translation, elongation , events occur which cause the protein/polypeptide to grow in length as additional amino acids are sequentially attached to one another. During elongation: the appropriate aminoacyl-tRNA molecules associates with the A site (aminoacyl binding site) on the large ribosomal subunit (this is called recognition ) a peptide bond forms between the amino acids at the P and A sites (this is called peptide bond formation ) the mRNA molecule moves along on the ribosome, thus repositioning the tRNA from the A site to the P site (this is called translocation ) steps 1-3 are repeated until a stop codon on the mRNA arrives at the A site 4. The third stage of translation, termination , occurs when the stop codon arrives at A site and a releasing factor associates with it, thus detaching the completed protein.
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tRNA is the adaptor molecule in protein synthesis with anticodon triplet that recognizes codons on mRNA template. tRNAs bring in the appropriate amino acid covalently attached to the adenosine 3’OH via an ester linkage. Translation – Overview Empty, uncharged tRNA Activated, charged amino-acyl tRNA Growing peptidyl tRNA 5’ 3’ 1 codon 1 anticodon 1 amino acid Protein synthesis at the ribosomes involves the interaction of two types of RNA: mRNA – message (has codons) and tRNA – decoder (has anticodons and covalently attached DNA is transcribed into many types of RNA: DNA tRNA DNA rRNA DNA snRNA DNA mRNA Protein
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Ribosomes are composed of proteins and rRNA , both of which are involved in structure and catalysis. 3. Although RNA is single stranded, does it have a specific 3D structure? 2. What are frameshifts in codon-anticodon interactions, and what effect do they have on protein synthesis?
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This note was uploaded on 09/01/2009 for the course BIO Bio 3390 taught by Professor Giovanni during the Spring '09 term at Benjamin Franklin Institute of Technology.

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Chapter30 - Biochemistry I Translation Protein Synthesis in...

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