ADL Lecture 2: 9 Flashcards
Translation
Translation
synthesis of protein by an mRNA originally copied from DNA
What are the two processes of protein production?
- information-transfer processes: RNA base sequence determines an amino acid sequence
- chemical processes: amino acids are linked together
Polypeptide chains
linear polymers of amino acids
How many amino acids are there in the genetic code?
20
*Amino acids are the building blocks of proteins
peptide bond
carboxyl group of one amino acid to amino group of next AA by hydrolysis
Ribosomes
“machines” that contain multiple ribosomal RNAs (rRNAs) and proteins
What are the three task ribosomes perform in bacteria/eukaryotes?
- bind mRNA and identify start codon (where translation begins)
- facilitate complementary base pairing of mRNA codons and the corresponding tRNA anticodons
- catalyze formation of peptide bonds between amino acids on growing polypeptide chain
What are the five major components of the translation system?
- mRNA
- Ribosome
- tRNA
- aminoacyl-tRNA synthetases
- initiation, elongation and termination factors
aminoacyl-tRNA snthetases
set of molecules catalyzes the attachment of particular amino acid to its corresponding tRNA molecule
tRNA (main action)
small adaptor molecule that translates codons into amino acid
Eukaryotic (E) translational initiation
- eukaryotic 40s ribosomal subunit complexes w/ eIF proteins
- eIFs & charged tRNA^met bind small subunit to form pre initiation complex
- complex recruited to 5’ region
- once complex is formed, it “scans” for start codon (AUG) Kozak sequence –> 60s subunit
elongation factors (EF) use what type of energy? and what do EFs perform?
GTP hydrolysis;
- recruit charged tRNAs to A-site
- Form peptide bonds btw sequential AA
- translocate ribosome in 3’ direction along mRNA
peptidyl transferase
catalyzes couple reaction in which bond connecting methionine to tRNA^met is transferred to amino group of next AA (=peptide bond)
what are the three stop codons?
UAA
UAG
UGA
Bacteria and eukaryotes use ___ to bind a stop codon in the __ site.
release factors (RF) A-site
iso-accepting tRNAs
tRNA molecules with different anticodons for the same amino acids
Post-translational polypeptide processing
modifies polypeptides into functional proteins by removal or chemical alteration of amino acids
Protein sorting/ signal sequences (leader sequences)
direct proteins to their cellular destinations
Chaperone Proteins
help proteins fold correctly and/or trigger destruction of incorrectly folded protein
What is the most common AA modification?
phosphorylation carried out by kinases
Incorrectly folded proteins cause mutations… what happens to these proteins?
Within the ER, proteins that are incorrectly folding are bound by molecules called chaperones that help proteins fold correctly (if folded correctly-released; in nor folded properly-destroyed)
