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Unformatted text preview: BIS101/Engebrecht S10 Outline09Lectures15-16 Prokaryotic Transcription, Translation and the Genetic Code Reading in 8th edition Chapter 8, 255-270; 9th edition Chapter 8, 295-304 I. Transcription = making RNA from DNA (Handout14Transcription Directionality) a. RNA polymerase b. Initiation i. Promoters, -10 and –35 ii. Closed vs. open promoter complex c. Elongation d. Termination – signals are in the RNA molecule (Handout15TranscriptonTermination) i. Rho-independent termination ii. Rho-dependent termination
Reading in 8th edition Chapter 9, 273-94; 9th edition Chapter 9, 319-344. II. Cracking the Genetic Code a. T4 suppressor experiment defines the basis for the genetic code b. Biochemical experiments decodes the words III. Translation = the process by which the code of the DNA, as it is transmitted by mRNA, is used to synthesize proteins. a. tRNAs and aminoacyl-tRNA synthetases. b. The codon:anticodon interaction between tRNA and mRNA, the wobble rules. c. The structure and function of the ribosome, rRNAs, ribosomal proteins, 30S and 50S subunits, Shine-Dalgarno sequence (base pairing between mRNA and 16S rRNA), initiation factors, formylMet-tRNAMet, ATG initiation codon, elongation factors, aminoacyl site and peptidyl site of the ribosome, termination factors, stop codons. d. Coupling of transcription and translation in E. coli. Translation components in prokaryotes-the information below is to help you when we discuss translation. This is not a list for you to memorize! 70S ribosome = the actively translating ribosome 30S ribosomal subunit = the small subunit of the ribosome. The major RNA component of the small subunit is the 16S rRNA. This is what binds to the mRNA via base pairing with the Shine Dalgarno sequences that lie 3-8 bases upstream of the initiating AUG (the start codon). 50S ribosomal subunit = the large subunit of the ribosome. Both the 23S rRNA and the 5S rRNA are components of the large subunit. The 23S forms the transpeptidylase activity that catalyzes peptide bond formation. tRNA = the adaptor that reads the triplet code on the mRNA and brings the correct amino acid to the ribosome. Aminoacyl-tRNA synthetases = the enzyme that “charges” the tRNA, that is, puts the amino acid onto the tRNA to be brought to the ribosome. Initiation Factors (IF1, IF2, IF3) = GTP binding proteins that provide the energy for protein synthesis. IF1 = exact role is unknown, is believed to participate in the recycling of the ribosome. IF2 = binds to the initiator fMET-tRNA and stimulates the binding of this molecule to the 30S subunit bound to the mRNA. The energy derived from GTP hydrolysis helps to drive the assembly of the two ribosomal subunits. IF3 = stimulates the binding of the mRNA to the 30S subunit. Elongation Factors (EF-Tu, EF-G and EF-Ts) = GTP binding proteins that provide the energy for protein synthesis. EF-Tu = mediates the entry of aminoacyl-tRNAs into the A site. EF-G = provides the energy for translocation. EF-Ts = mediates the release of EF-Tu from the ribosome. Release Factors (RF1, RF2, RF3) RF1 = recognizes the triplet stop codon UAA and UAG and binds to the A site. RF2 = recognizes the triplet stop codon UAA and UGA and binds to the A site. RF3 = helps RF1 and RF2 catalyze chain termination. ...
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This note was uploaded on 07/02/2010 for the course BIS BIS 101 taught by Professor Sanders during the Spring '09 term at UC Davis.
- Spring '09