L20 Translation - Translation

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Translation http://genome.imim.es/courses/Madrid04/exercises/ensembl/images/ribosome.jpg 1 Last time ✤ Proteins that affect gene transcription: Transcription Factors ✤ Classes (types) Anatomy of a transcription factor How specific transcription factors work ✤ ✤ ✤ Post transcriptional regulation: mRNA stability ✤ The role of the Poly A tail RNA interference (RNAi) 2 ✤ Translation ✤ from mRNA to proteins ✤ quick review: features of proteins ✤ Important components of translation machinery ✤ tRNA ✤ ribosomes ✤ Revisiting translation (with some detail) elongation, termination ✤ Initiation, 3 Translation Process by which information in mRNA is translated to amino acid sequence 4 5 Finding the Rosetta Stone INPUT (RNA) UUU UUU, etc AAA AAA, etc OUTPUT (aa) Phenylalanine Lysine 61/64 combinations code for amino acids What do the last 3 codons code for? STOP (UAA, UGA, UAG) AUG codes for START and for Methionine. Marks start of reading frame….. en.wikipedia.org 6 The Start codon (AUG) determines reading frame 3 possible reading frames, only ONE is correct (usually). the bad cat ate the red rat (English) aug uua ccc uua aua ccg uga (RNA) heb adc ata tet her edr ugu uac ccu uaa uac cgu Stop codon! no stop codon! 7 The key to the genetic code Note that the code is both redundant and unambiguous 8 A protein ‘refresher’ N C 9 10 Four levels of protein structure primary secondary tertiary quaternary (not all proteins) 11 Important components of translation machinery a bit more detail on tRNA and ribosomes http://biology.unm.edu/ccouncil/Biology_124/Images/RNAtranslation.jpeg 12 tRNA - the translator tRNA binds codons in mRNA, and carry associated amino acid 13 Features of tRNA stem loops modified bases anti-codon acceptor stem inosine 14 There are ~45 tRNAs ✤...but there are 61 codons coding for 20 amino acids. How does this work? ✤ the third base wobble. 15 Third base wobble Sometimes the 3rd base in the codon doesn’t matter too much - “relaxed pairing” Leucine codons: Glycine codons: CUU GGU CUC GGC CUA GGA CUG GGG (UUA) (UUG) inosine Wobble ‘rules’ in Fig. 13.14 16 tRNAs are ‘charged’ with a specific amino acid charged amino acid Aminoacyl-tRNA synthetase attaches a specific amino acid to tRNA 17 Ribosomes carry out translation http://www.emc.maricopa.edu/faculty/farabee/BIOBK/ribosome.gif 18 A closer look at ribosomes 2 subunits Protein + RNA RNA is catalytic tRNA occupy 3 ‘slots’ 19 Closer look at subunits 20 tRNAs fit into 3 slots in large subunit 21 Translation in bacteria ✤ Initiation ✤ assembly of proteins ✤ Elongation ✤ protein synthesis ✤ Termination ✤ dissociation of translation machinery 22 Initiation (bacterial) step 1 23 The Shine-Dalgarno sequence 9nt sequence of mRNA that binds 16S rRNA in ribosome! 24 Initiation (bacterial) step 2 step 3 25 Eukaryotic initiation G C C (A/G) C C A U G G Kozak’s Rules (start consensus sequence) 26 Elongation (bacterial) new tRNA comes in aa chain transfered to tRNA in A site 27 Elongation (bacterial) tRNA in E site leaves 28 Termination (bacterial) stop! 29 Polyribosomes 30 Summary ✤ mRNA sequence is translated into amino acid sequence ✤ Amino acids are joined by peptide bonds, and contain R groups, which give them specificity ✤ tRNA is the ‘translator’ molecular, binding mRNA codons and carrying specified amino acid Ribosomes (lg/sm subunit) are composed of both protein and RNA (catalytic) Initiation, Elongation and Termination are the three stages of translation 31 ✤ ✤ Ungraded problems ✤ ✤ Look over Chapter 13 S2, S4, S5 Try Chapter 13: C1, C2, C7, C10, C14, C23, C28 32 Next Time Gene mutation 33 ...
View Full Document

This note was uploaded on 03/29/2009 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas at Austin.

Ask a homework question - tutors are online