9. Proteins And Their Synthesis Flashcards
Prokaryotic vs. eukaryotic transcription and translation
Prokaryotes:
RNA not processed
Translation on site
Eukaryotes:
RNA processed
Translation following RNA transport
Ribosomes
Decoding hubs
Prokaryotes:
Small subunit: 30S
Large subunit: 50s
Eukaryotes
Small subunit: 40S
Large subunit: 60S
RRNA
Folds up by intramolecular base pairing
TRNA
Transfer RNAs
Small adapters between amino acids and codons in mRNA molecules
Anticodon of tRNA base pairs with codon of mRNA
Amino acid covalently attached to 3’ end of tRNA
Often contain modified nucleosides
Aminacyl-tRNA synthetase
Attaches an amino acid to its specific tRNA
Codon specifies resides in tRNA, NOT attached to amino acid
Ribosomal domains
APE
Aminoacyl binding site
Peptides binding site
Exit binding site
Steps of translation
1) polypeptide chain initiation
2) chain elongation (peptide bonds)
3) chain termination
Shine-dalagarno sequence
MRNA and ribosomal recognition in prokaryotes; aligns at p-site
Prokaryotes initiation factors
IF 1
IF 2
IF 3
Translation initiation in prokaryotes
Initiation factor
1st ATG recognized and bound to MET at P site
MET tRNA associates to 40S subunit
40S scans for 1st AUG and binds
Initiator factors leave
Large subunit assembles AUG positioned at P-site
Termination: release factors
Prokaryotes:
RF 1, 2, 3
Eukaryotes:
ERF
Initiation stage (steps)
Binding of MET-tRNA to mRNA and small subunit of ribosome
Large subunit combines with small subunit
Elongation stage (steps)
Incoming aminoacyl tRNA fits into A-site
Bond formed between methionine and amino acid molecule on tRNA
Repeated until amino acid chain is formed
Termination stage (steps)
Ribosomes reaches stop codon
Amino acid chain detaches from ribosome
TRNA and ribosomal subunits dissociate from mRNA
How is frame established?
1st ATG (MET) in the mRNA establishes frame