BIO325 - Lecture 9

BIO325 - Lecture 9 - BIO325 Translation Cont I Translation...

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BIO325 February 12, 2008 Translation Cont. I. Translation a. Ribosomes i. Function – translate mRNA to make protein ii. Structure – rRNA, ribosomal proteins, ribosomal subunits iii. Problem 1. How can it make itself? 2. Evolutionary“Chicken and Egg” Problem 3. New cell always has plenty of ribosomes to start with to make proteins including ribosomal proteins which are components of ribosomes 4. Answer? a. rRNA first worked independently of proteins, that is to say ribosomes were once entirely rRNA b. Proteins came along the way to make proteins work better iv. rRNA are relatively large, proteins relatively small v. After assembled, ribosome is 2/3 rRNA by mass, 1/3 protein vi. Ribosome – “ribose body”, mostly rRNA vii. rRNAs form Ribosome shape, ribosomal proteins are studded in crevasses in rRNA folds (stabilize structure, but don’t define it) viii. No basic step of translation that is carried out with ribosomal protein as a major factor ix. Structure and basic functions are rRNA, not protein 1. Proteins increase efficiency and accuracy by stabilizing structure 2. Just enhancing overall function (not basic functions) b. Prokaryotic Translation i. Initiation 1. Small subunit (30S) a. Contains 16S rRNA b. IFs (Initiation Proteins/Factors) i. Not ribosomal proteins ii. Come during initiation and leave after 2. + mRNA a. Bind together by mostly complementary base pairing (not protein interaction) between 16S rRNA and small conserved sequence on mRNA (Shine- Dalgarno sequence) i. Consensus 1. AGGAGG b. Found on upstream area of start codon called 5’
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untranslated region c. Helped by IF-3 i. Assists in binding of 30S and Shine- Dalgarno sequence 3. + tRNA (in P site)
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This note was uploaded on 04/22/2008 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas.

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BIO325 - Lecture 9 - BIO325 Translation Cont I Translation...

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