IUB BIOL-L 211 - Translation I (3 pages)

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Translation I



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Translation I

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Termination of last lecture; Covers translation initiation in both prokaryotes and eukaryotes


Lecture number:
31
Pages:
3
Type:
Lecture Note
School:
Indiana University, Bloomington
Course:
Biol-L 211 - Molecular Biology
Edition:
1
Documents in this Packet
Unformatted text preview:

BIOL L211 Lecture 31 Outline of Last Lecture I Article II Translation III Ribosome Composition Outline of Current Lecture I Recruiting Ribosome to mRNA transcript II Initiation of Prokaryotic Translation III Initiation of Eukaryotic Translation IV Eukaryotic Translation Current Lecture Translation I I Recruiting Ribosome to mRNA transcript A Prokaryotes 1 Ribosomal Binding Site RBS consensus sequence 3 9 bp upstream of the start codon recognized bound by ribosomes 2 In prokaryotes consensus is 5 AGGAGG 3 B Eukaryotes 1 5 cap responsible for recruitment of ribosome 2 After recruitment ribosome binds and scans to find the start codon codon 3 Kozak Sequence eukaryotic consensus sequence that increases the efficiency of translation includes bases upstream and downstream of the start includes AUG C Note that the start codon must always be placed in the P site These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute E Polysome Translation efficiency can be increased with the binding of multiple ribosomes polyribosomes increases protein output from a given transcript 1 Each ribosome can only produce one protein at a time II Initiation of Prokaryotic Translation A Initiator tRNA prokaryotes specialized with a methionine with a formyl group attached fMet 1 Anticodon and start codon pair in P site B Initiation Factors IF proteins that facilitate translation initiation in prokaryotes 1 IF1 Binds A site prevents tRNA from entering A site 2 IF2 Binds IF1 and will with GTP help recruit initiator tRNA to bind to the small subunit after IF3 is in place 3 IF3 Binds E site prevents tRNA from entering E site C Initiator tRNA and mRNA recruited to small ribosomal subunit 1 rRNA component of ribosome recognizes RBS and binds base pairs 2 Start codon at P site 3 Initiator tRNA comes to P site 4 After mRNA and tRNA are recruited large subunit comes 5 IF1 IF2 and IF3 leave III Initiation of Eukaryotic Translation A Eukaryotic Initiation Factors eIF proteins that facilitate translation initiation in eukaryotes 1 eIF1 eIF1A and eIF5 block A and E sites so that charged initiator tRNA can enter P site a Note In eukaryotes initiator tRNA has just an ordinary Met no fMet the 2 eIF4E binds the 5 cap of mRNA cooperates with other mRNA associated initiation factors to interact with ribosome associated initiation factors in small subunit B Initiator tRNA is aligned in P site 1 Small ribosomal subunit and its eukaryotic initiation factors search mRNA 5 to 3 for start codon 2 Once found large subunit recruited 3 eIFs leave E and A sites and translation begins IV Eukaryotic Translation A Circular Structure 1 eIF4G protein that interacts with the poly A tail and poly A binding proteins to make a ring structure of mRNA to facilitate translation a Helps binding of eIF4E b Helps recruit large subunit c Makes translation more efficient d Limits degradation eventually degrades anyway


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