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BCMB 415 > Translation > Flashcards

Translation Flashcards

1
Q

mRNA

A

Codons for amino acids

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2
Q

tRNA

A

Anticodons: Bring amino acids to ribosomes

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3
Q

Aminoacyl-tRNA synthetases

A

-Charges tRNAs with specific amino acid
-Recognize tRNAs by features of the acceptor stem and anticodon loop
-One amino acid could have more than one tRNA
-Only one tRNA synthetase per amino acid

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4
Q

Ribosomes

A

-Site of protein synthesis; brings mRNA and charged tRNA together
-They do not recognize the amino acid the tRNA’s carry

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5
Q

Open Reading Fram (ORF)

A

Start codon, stop codon, long chain

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6
Q

Polycistronic

A

More than one ORF:
-Prokaryotes=Polypeptides encoded by a polycistronic mRNA perform related functions
-Eukaryotes=Monocistronic RNAs encode a single ORF

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7
Q

Ribosome binding site (RBS)/Shine-Dalgarno sequence

A

Base pairs of16s rRNA

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8
Q

Eukaryotic Efficient translation

A

-5’ cap that recruits ribosome
-Kozak sequence of purines (A/G) upstream of start
-Poly-A-Tail allows the recycling of ribosomes

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9
Q

Cloverleaf structure

A

(tRNA’s appear as an L-shape in 3-D) -D loop, Pseudouridine loop, Acceptor arm takes the amino acid, Anticodon loop has the anticodon that pairs with the codon in the mRNA

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10
Q

Modified Bases in tRNA

A

uridine, pseudouridine, dihydrouridine

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11
Q

tRNA charging reaction

A
  1. Adenylylation of the amino acid
  2. Transfer of amino acid to tRNA
    -Both events are catalyzed by aminoacyl-tRNA synthetase
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12
Q

Correct Amino Acid

A

-The frequency of a wrong amino acid is less than 1 in 1000
-Aminoacyl-tRNA synthetase can only accommodate a particular amino acid in its activation center by forming bonds it can recognize
- If one does slip by aa-tRNA synthetases have an editing site that can cleave the wrong charged amino acid

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13
Q

Prokaryote vs Eukaryotes

A

-Prokaryotes have their transcription and translation coupled together
-Eukaryotes have their transcription and translation take place in two different compartments

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14
Q

Peptide Bonds

A

Formed by the peptidyl transferase center in the ribosome interaction between two charged species of tRNAS. The bond is broken between the peptidyl-tRNA and the polypeptide chain. Takes place at the 3’end of the chains
-Catalyzed by 23S rRNA

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15
Q

Ribosome Sites

A

-A-site has the aminoacyl site where the charged tRNA enters
-P-site is the peptidyl site where the tRNA is linked to the growing polypeptide chain
-E-site is the exit site where the t-RNA is about to leave the ribosome

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16
Q

Initiation of Translation in E.Coli

A
  1. 30s ribosome binds to the mRNA
  2. Shine-Dalgarno sequence of mRNA base pairs with the 16s rRNA
  3. The initiating tRNA is charged with formil-Met
  4. IF3 binds to the 30s ribosome
  5. IF1 and GTP-bound IF2 join the 30s ribosome
  6. IF3 leaves the 30s complex
  7. 50s subunit joins the 30s initiation complex stimulating hydrolysis of GTP by IF2
  8. Complex can now accept the tRNA in the A site
17
Q

Initiation Factors/ Eukaryotic Initiator Factor

A

-IF1- prevents tRNA from binding to the A-site
-IF2- is a GTPase, that prevents charged-tRNA from the 30s to ensure proper initiator tRNA
-IF3- binds the small subunit on the exit site

18
Q

Initiation complex in Eukaryotes

A
  1. eLF4B stimulates the helicase activity of elF4A to form the 48s pre-initiation complex
  2. 48s scans the mRNA to find the AUG codon (ATP dependant)
  3. Codon-anticodon produces a conformation change on elF5 that leads to elF2 to hydrolyze GTP
  4. 60s unit attaches on top to create the full 80s ribosome
19
Q

Elongation Factor Tu (EF-Tu)

A

-Delivers aminoacyl-tRNAs to the A site

20
Q

Correct tRNA anticodon

A

-Decreased affinity, correct tRNA’s undergo accommodation

21
Q

Translocation

A

The tRNA complex and ribosome move towards the 3’ end of the mRNA

22
Q

Elongation Factor-G (Ef-G)

A
  1. GTP domain on EF-G binds to the 50S ribosome
  2. ER-G binds with the 30S subunit
  3. Hydrolyzes the GTP domain causing a conformation change in the A site
    4.To accommodate the arm the peptidyl tRNA at the A site is pushed to the P site carrying the mRNA
  4. EF-G dissociates
23
Q

Peptide bond formation

A

2 GTP + 1 ATP

24
Q

Termination

A

Release Factors
-Class 1
-RF1 recognizes UAG
-RF2 recognizes UGA
-UAA is recognized by Both
-eRF1 recognizes all the three stop
-Class 2
- RF3 is a GTP binding protein required to release Class 1 RFs from the ribosome after termination of translation

25
Q

RF1

A

-Structure of the RF1 bound to the ribosome shows that specific amino acids pair with the bases of the stop codon

26
Q

Ribosome recycling Factor (RRF)

A

RRF and EF-G are necessary for the dissociation of small and large subunits

BCMB 415 (1 decks)

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