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14 Cards in this Set
- Front
- Back
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How does insulin affect the CAP binding complex?
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Insulin bind to and inactivate PHAS-1 receptors by phosphorylate them. When insulin is absent, PHAS-1 can sequester the mRNA CAP, preventing translation.
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eIF4 is a subunit of the CAP complex. When is it found in unusual high amounts?
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Cancer, when translation is unregulated and tumors grow rapidly.
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One of the first steps in translation is the charging of tRNA's. How does this occur?
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Aminoacyl-tRNA Synthetase can bind tRNA, ATP, and the AA. It adenylates the AA, and cleaves ATP to AMP and PPi to form a high energy ester bond between the tRNA and AA. (This high energy bond is used later to form peptide bonds).
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The first tRNA-AA pair to come into the _____ site is the ______ t-RNA. It is escorted to the ribosome complex via ______.
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P; Met; eIF2
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T/F: the anticodon sequence of the tRNA is not as important as the size of the tRNA molecule during translation recognition.
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True.
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When the start codon ______ is recognized, _______ leaves, and elongation begins.
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AUG; eIF2
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How does the prokaryotic and eukaryotic translation mechanisms know which AUG is the start codon?
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Prokaryotes: Shine Dalgarno
Eukaryotes: Kozak |
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Why do prokaryotes have polycistronic mRNA?
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Because each AUG with a Shine Dalgarno sequence is recognized as a start codon, whereas in eukaryotes, only the first AUG by a Kozak sequence is recognized as the start codon.
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In forming a new peptide bond, the N-terminus in the ______ site attacks the C-terminus in the ______ site.
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A; P
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What does peptidyl transferase do?
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It forms peptide bonds between the amino acids in the A and P sites. It uses energy from t-RNA charging.
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What are the functions of EF1 and EF2 (EF = elongation factors).
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EF2: translocates the ribosome to the next codon
EF1: brings next tRNA-AA into A site *each hydrolyzes one GTP for energy! |
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The stop codon ______ recruits release factor binding to _______ site, inhibiting any more translation.
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UAG; A
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How does a stress signal cause translation to stop momentarily?
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A stress in the ER (large range of stresses) induces PERK to phosphorylate eIF2, so that it cannot bring in first Met-tRNA. Chaperones may also be recruited.
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How do miRNA's work?
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These are short non-coding "hairpin" RNA's that base pair with mRNA while at the same time interact with RISC, to sequester mRNA from translation. If they have strong complementarity with mRNA and are to be degraded, they are sent to either the exosome (3' to 5') or XRN1. If they bind weakly, they are sent only to XRN1 (and degraded 5' to 3')
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