Protein Translation Flashcards
Define Translation
Biological polymerization of amino
acids into polypeptide chains
Translation requires what 4 features?
- Amino acids
- mRNA
- Ribosomes
- tRNA
Define Transfer RNAs
- Adapt genetic information present as specific triplet codons in mRNA to corresponding amino acid
- tRNA anticodons complement mRNAs
- tRNAs carry corresponding amino acids
Prokaryote ribosomes are ___S.
Eukaryote ribosomes are ___S.
Prokaryote: 70S
Eukaryote: 80S
Explain rDNA
- rRNA genes
- Moderately repetitive DNA fraction present in clusters at various chromosomal sites
- Each cluster contains tandem repeats separated by noncoding spacer DNA (These spacer regions are used to identify the type of organism we have)
Why do we even need these repetitive regions present?
We need ribosomes present all the time because we make a plethora of different molecules. We ALWAYS need to have ribosomes present
Define tRNA
- Small in size and very stable
- 75–90 nucleotides
- Transcribed from DNA
- Contain posttranscriptionally modified bases
- tRNAs have a cloverleaf structure
What is the 3 bases that will be found always at the 3’ end of tRNA
CCA
Explain Anticodon
- tRNA has anticodon that complementarily base-pairs with codon in mRNA
- Corresponding amino acid is covalently linked to CCA sequence at 3′ end of all tRNAs
Explain Aminoacylation
- Known as tRNA charging
- Before translation can proceed, tRNA molecules must be chemically linked to respective amino acids
- Aminoacyl tRNA synthetase: Enzyme that catalyzes aminoacylation
- 20 different synthetases, one for each amino acid
- Highly specific; recognize only one amino acid
What is the difference between prokaryotes and eukaryotes in terms of the methionine.
methionine that starts as first is a formylmethionine. ONLY the first one in bacterial synthesis. In eukaryotes, it is just methionine
Undertsand the site of the rubosome in terms of A, P, and E site
A site: Aminoacyl attachment
P site: peptide bond formation
E: Exit site
For the 3 stop codons, is there a tRNA corresponding with the anticodon?
NO!
What 6 things does Initiation require?
- Small and large ribosomal subunits
- mRNA molecule
- GTP
- Charged initiator tRNA
- Mg2+
- Initiation factors
T/F: Only the initiator sequence AUG will go in through the P site. Everything else goes in through the A site
TRUE!
Explain Shine-Dalgarno sequence
- AGGAGG
- Precedes AUG start codon in bacteria
- Matches up with the 16S rRNA starting initiation
What makes up the initiation complex of prokaryotic translation
- Small ribosomal subunit + initiation factors + mRNA at codon AUG
- Combines with large ribosomal subunit
Polycistronic messages are always in what type of system?
Prokaryotic because we make multiple “messages” aka genes that are coded
In Eukaryotic genes, we have what type of system?
- Monocistronic
- Only one gene is regulated by that one operon.
What are the 3 STOP codons?
UAA
UGA
UAG
What is 23S rRNA known as?
- Ribozyme with the catalytic activity of peptidyl transferase
- Catalyzes peptide bond formation between amino acid on tRNA at A site and growing peptide chain bound to tRNA in P site
What are GTP-dependent release factors?
Stimulates hydrolysis of polypeptide
from peptidyl tRNA—released from
translation complex
What are Polysomes (or polyribosomes)
- mRNAs with several ribosomes translating at once
- As mRNA passes through ribosome, its free to associate
with another small subunit
Every amino acid has what properties?
- Carboxyl group
- Amino group
- R (radical) group bound to central carbon atom
How is a peptide bond formed?
Dehydration (condensation) reaction between carboxyl group and amino group
Explain the primary structure of a protein
Only sequence of amino acids
Explain the Secondary protein structures
a-helix and B-pleated sheets
Explain the Tertiary Protein structures
3-D conformation of a SINGLE protein
Explain the Quaternary structure
Composed of more than one polypeptide chains
