Translation Seminars and Conversational Class | Quizlet

What is translation?

Synthesis of protein from mRNA using ribosomes

Direction of mRNA reading

5′ → 3′

Direction of protein synthesis

N-terminus → C-terminus

Start codon

AUG (Methionine)

Stop codons

UAA, UAG, UGA

How many codons exist?

64

How many code for amino acids?

61

What is degeneracy of genetic code?

Multiple codons code for same amino acid

Which amino acids have only one codon?

Methionine and Tryptophan

What is the genetic code property "non-ambiguous"?

Each codon codes for only one amino acid

What does "commaless" mean?

No gaps between codons

What is a reading frame?

Grouping of nucleotides into triplets starting at AUG

What causes frameshift mutation?

Insertion/deletion of 1-2 nucleotides

Silent mutation effect

No amino acid change

Missense mutation effect

Different amino acid

Nonsense mutation effect

Premature stop codon

What is tRNA function?

Delivers amino acids to ribosome

tRNA amino acid attachment site

3′ CCA end

Bond between amino acid and tRNA

Ester bond

What is anticodon?

3-base sequence complementary to mRNA codon

What is wobble rule?

Flexibility at 3rd codon position allowing fewer tRNAs

Wobble pairing: inosine pairs with

A, U, C

Wobble pairing: G pairs with

C or U

What enzyme charges tRNA?

Aminoacyl-tRNA synthetase

Energy used in tRNA charging

ATP → AMP + PPi

Why is aminoacyl-tRNA synthetase important?

Ensures translation accuracy

What is proofreading in this enzyme?

Removes incorrect amino acids

Ribosome function

Site of protein synthesis

Prokaryotic ribosome

70S (30S + 50S)

Eukaryotic ribosome

80S (40S + 60S)

Small ribosomal subunit function

Binds mRNA and ensures accuracy

Large ribosomal subunit function

Catalyzes peptide bonds

Ribosome A site

Binds incoming aminoacyl-tRNA

Ribosome P site

Holds growing peptide chain

Ribosome E site

Exit site for empty tRNA

What is peptidyl transferase?

rRNA enzyme forming peptide bonds

Is peptide bond formation energy-dependent?

No (driven by high-energy tRNA bond)

What is initiation?

Assembly of ribosome on mRNA

Initiator tRNA binds which site?

P site

Initiator amino acid in eukaryotes

Methionine

Initiator amino acid in prokaryotes

N-formylmethionine (fMet)

Prokaryotic start recognition

Shine-Dalgarno sequence

Eukaryotic start recognition

5′ cap scanning + Kozak sequence

What is Kozak sequence?

Consensus sequence around AUG improving initiation

What is elongation?

Addition of amino acids to growing chain

Factor delivering tRNA (eukaryotes)

eEF1α-GTP

Factor for translocation (eukaryotes)

eEF2-GTP

What is translocation?

Ribosome moves 3 nucleotides along mRNA

What is polysome?

Multiple ribosomes translating one mRNA

What triggers termination?

Stop codon in A site

What binds stop codon?

Release factors

Result of termination

Protein released + ribosome dissociates

Energy used in translation

GTP (elongation + initiation)

Energy used in tRNA charging

ATP

What is SRP?

Signal recognition particle directing protein to ER

Function of signal peptide

Targets protein to RER

Where do secreted proteins get synthesized?

Rough ER

Where are cytosolic proteins synthesized?

Free ribosomes

What happens in Golgi?

Protein modification and sorting

Examples of post-translational modifications

Phosphorylation, glycosylation, hydroxylation, lipidation

What is ubiquitination?

Tagging protein for degradation

What is proteasome?

Degrades ubiquitinated proteins

What is UPR?

Response to unfolded proteins in ER

What does eIF2 phosphorylation do?

Inhibits translation initiation

What regulates ferritin translation?

Iron via IRP binding to mRNA

What regulates globin synthesis?

Heme via HRI kinase

Effect of diphtheria toxin

Inhibits eEF2 → stops translation

Streptomycin effect

Blocks initiation + misreading

Tetracycline effect

Blocks A site entry

Chloramphenicol effect

Inhibits peptidyl transferase

Erythromycin effect

Blocks translocation

Puromycin effect

Causes premature termination

Why is wobble important?

Reduces number of required tRNAs

What happens if one amino acid is missing?

Translation stops

Why is translation high-energy?

Requires ATP and GTP

What ensures correct codon-anticodon pairing?

Ribosome + tRNA specificity

What determines protein final destination?

Signal sequences

What is NLS?

Nuclear localization signal

What targets proteins to mitochondria?

N-terminal amphipathic helix

What targets proteins to peroxisomes?

C-terminal signal sequence

Which inhibitors act on 30S ribosomal subunit?

Streptomycin, Tetracycline

Which inhibitors act on 50S ribosomal subunit?

Chloramphenicol, Erythromycin, Clindamycin

Which antibiotic causes misreading of mRNA?

Streptomycin

Which antibiotic blocks aminoacyl-tRNA entry?

Tetracycline

Which antibiotic inhibits peptidyl transferase?

Chloramphenicol

Which antibiotic blocks ribosomal exit tunnel?

Erythromycin

Which antibiotic mimics tRNA?

Puromycin

Which antibiotic affects mitochondrial ribosomes?

Chloramphenicol

Which antibiotic works in both prokaryotes and eukaryotes?

Puromycin

Which drug class includes clindamycin?

Lincosamides

What does clindamycin inhibit?

Peptidyl transferase or translocation