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Flashcards in Protein Synthesis Deck (13):
1

What are the three main principles of ribose functioning

1. Two unequal separable units
2. Compact cores of each subunit are formed by self-folding specific rRNA molecules
3. Multiple ribosomal proteins decorate compact rRNA cores

2

Initiation

1. mRNA and initiation factors IF-1 and IF-3 bind to 30S subunit
2. Initiator formylmethionine-tRNA in complex with IF-2 and GTP binds to the P site of the 30 subunit.
3. Large 50 S Subunit companies with the 30S subunit forming the initiation complex

3

Ternary Complex

Aminoacyl-tRNA + EF-Tu + GTP

4

Elongation

1. Formation of the ternary complex
2. Ternary complex binds to the A site - decoding step
3. GTP hydrolysis, EF-Tu-GDP leaves ribosome and new aminoacyl-tRNA comes to A site
4. N-formyl-methionyl group is transfered from its tRNA in the P site to A Site- Poptideyl Transferase Reaction
5. EFG-GTP catalyzes transition of ribosome by one codon towards 3 end of mRNA clearing A site for next- Translocation

5

The Shine-Dalgarno Sequence

A ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG. The RNA sequence helps recruit the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon.

6

Initiator amino acid in Eukaryotes and prokaryotes

Eukaryotes: methionine
Prokaryotes: N-formylmethionine

7

Termination

1. Release factors recognize the stop codons
- RF1 (UAA and UAG)
RF2- (UAA and UGA)
These factors hydrolyze the bonds between tRNA and peptide
2. Peptide and tRNA leave the Ribosome
3. RRF (Recycling release factor) with RF3 cause ribosome to dissociate.

8

Where can proteins be targeted to ?

Ribosomes

9

Signal recognition Particle

Recognizes the signal sequence that comes from the ribosome. Ribonuclic protein molecule that temporarily pauses the translation.

10

Nuclear Proteins

Nuclear Localization sequence (NLS)

Not cleaved after protein targeted

11

Protein Degradation in Eukaryotes

Proteins that should be degraded are linked to small extremely conserved protein ubiquitin which acts as a tag

12

26S Proteasome Complex

Cleave the ubiquinated proteins: Degrade proteins with this tag

13

N terminal Amino Acid Stability rule

N-terminal amino acid of a protein determines its half-life (likelihood of being degraded).