Protein Translation Flashcards by Nastassia Pearcy

What is a nuclear pore receptor?

finds nuclear pore binding site and uses ATP to get mRNA out
needed for macromolecules, including finished mRNAs

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What is nuclear pore complex?

Aqueous channel from nucleus to cytoplasm
Diffusion for small molecules only (<50K daltons)

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Does rRNA need a protein?

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What forms around the gene cluster of 18S, 5.8S, & 28S?

Nucleolus forms around this gene cluster

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Where does the rRNA (5S) get imported into?

the nucleolus

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Where is telomerase RNA found?

nucleolus

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What creates the large subunit of a ribosome?

5.8S, 28S, & 5S rRNAs

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What creates the small subunit of a ribosome?

18S rRNA

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What has many copies of the same DNA sequence for rRNA?

rDNA

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Why is redundancy expected?

because there are 64 combinations of 3 NT possible, but only 20 amino acids

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How many anticodons/tRNAs do we have?

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What are common features of many cancers?

Frame shift mutation & truncated proteins

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What has a template independent addition of CCA?

tRNA

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What is the structure of tRNA?

cloverleaf

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What is important to note about tRNA?

20 amino acetyl transferase enzymes that only charge each tRNA with one amino acid, the amino acid is specific to the different tertiary stuctures

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Where is the wobble position?

at 5’ tRNA position (3’ mRNA position)

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What is important for a wobble base?

inosine

What helps with wobble & provide binding sites for aminoacyl-tRNA synthetases?

tRNA base modifications

What allows for wobble?

modification on the tRNA molecule

What is specific for a particular amino acid?

tRNA synthetase

What happens if an incorrect amino acid is added?

it will end up in the editing site (of the tRNA synthetase) and it will get degraded/hydrolyzed

During peptide bond formation, where is the new peptidyl-tRNA molecule atatched to?

C terminus of growing polypeptide chain

What are the steps of peptide growth in the ribosome?

P site holds the proceeding tRNA w/ AA (3), the A site holds the new tRNA with the next AA (4)
The amino group of AA 4 attacks the carboxy grp of AA 3 to create a new peptide bond
tRNA that once held AA 3 moves to the E site, the P site holds the newly attached AA 4 tRNA (the tRNA and AA still attached until next attacks)
tRNA that once held AA 3 leaves the ribosome and the process continues growing the poly peptide from N-terminus to the C-terminus, linking each AA with a peptide bond

What is peptide bond formation catalyzed by?

rRNA

Are ribosomes a ribozyme?

yes because they have catalytic energy and bring 10^7 fold increase in reaction rate

How does tetracycline (antibiotic) inhibit protein synthesis?

Binds to bacterial 30s or 50s ribosomal subunit-> this prevents the attachment of aminoacyl-tRNAs to the acceptor site of the ribosome

What is the mechanism of tetracycline resistance that is related to ribosome function?

Tet (M,O,Q,S) are bacterial resistance genes that make a cytoplasmic proteins to interact with ribosomes-> this makes it insensitive to tetracycline

What can help stabilize the codon-anticodon interaction?

rRNA

What are the important initiation factors of ribosome assembly?

* One that binds to the poly A tail binding proteins * Another that binds the CBC (eIF4E)

rRNA can help to stabilize what?

stabilize the codon-anticodon interaction

How do Met & IF travel along the mRNA?

using ATP

What is GTP used for in GTP assembly?

for bringing the amino acid to the ribosome

If there is no GTP, can translation occur?

What preferentially dissociates?

incorrectly base-paired tRNAs

What are the steps for ribosome assembly & initiation?

1. An initiation factor (IF) w/ bound GTP is attached to a initiator tRNA (with Met), w/ the small ribosomal subunit it moves along mRNA with ATP until the start codon is reached 2. the initiation factor with GTP can be released and the large subunit of the ribosome binds to the small 3. Elongation factors continue to bring in the proper tRNAs, with the help of GTP 4. Once one of the 3 stop codons (UAG, UAA, UGA) are reached, a releasing factor helps bring translation to an end

What are the roles of rRNA i the ribosome?

* Forms overall structure * Forms the A, P, and E sites * Stabilizes codon-anticodon base pairing * Catalyzes peptide bond formations

What blocks translation partway through the polypeptide formation to create N terminus fragments due to the C terminus not being made as yet?

puromycin

What are the antibiotics that interfere with translation?

* puromycin ->causes premature re;ease of nascent polypeptides chains by its addition to growing end * tetracycline -> blocks binding of aminoacyl-tRNA to A site fo ribosome * macrolides

What is the purpose of caperone proteins?

* use ATP/heat from folding too early * heat shock proteins involved

What is an example of a chaperone protein?

HSP70 that coats polypeptide when it needs to prevent initial folding

What are the 3 phases of protein folding?

* correctly folded without help * correctly folded with help for molecular chaperone * incompletely folded & digested by the proteasome

Does rRNA have repeats?

yes