Flashcards in Protein Translation and Post-Translational Processing Deck (37)
Do both subunits of ribosomes have enzymatic function? If not, which one does?
No, only large subunit does
What is the ternary complex?
eIF2a-GTP bound to initiator methionine-tRNA
What is the pre-initiation complex?
ternary complex bound to small subunit + mRNA
What is the initiation complex?
pre-initiation complex bound to large subunit
The energy needed to bind to large subunit comes from what?
hydrolysis of eIF2a-GTP
What site is methionine-tRNA in?
P site of large ribosomal subunit
How much energy is required to elongate one amino acid?
2 GTP is needed: one to bind tRNA to the A site (charged tRNA) and another to move ribosome one codon over
When does translation terminate?
once a stop codon has reached the A site
What pairs with the stop codon in termination of translation?
a protein, eRF (eukaryotic release factor)
Does termination of translation require energy?
yes, when the peptide is release from the P site, provided by the hydrolysis of eRF-GTP
- ribosomal subunits separate from each other
Which antibiotic binds to ribosomes and causes mistranslation of codons?
neomycin and gentamicin
Which antibiotic binds to small subunit and inhibits initiation?
- also causes mistranslation
What anitibiotic prevents peptidyl bond formation?
Which antibiotic blocks the A site and prevents rRNA binding?
Which toxin removes adenine bases from various positions of the rRNA in the large subunit?
Which toxin inactivates EF-2 by ADP-ribosylation?
What are two ways to regulate translation (gene expression)?
1) prevent recognition of start codon by binding a protein to the 5' UTR of mRNA
2) phosphorylate eIF-2a (initiating factor), becomes inactive
Where does protein folding occur (organelle)?
cytosol and ER
Where does N-linked glycosylation occur?
ER, before protein folding is complete
In N-linked glycosylation, sugar is added to what residue in protein?
Where is dolichol phosphate located (organelle)?
Where does modification of oligosaccharide occur?
1) high mannose type (bulky)
2) complex type
What disorder affects N-linked glycosylation?
congenital disorder of glycosylation (CDG)
Which disorder has defective trimming of oligosaccharide chain?
Which disorder has defective synthesis of lipid-linked oligosaccharide precursor?
Where does O-linked glycosylation occur?
Which residues are sugar added to in O-linked glycosylation?
glycosyltransferases transfer sugars to serine or threonine of fully folded proteins
What is the first sugar of O-linked glycosylatoin?
What sugar does the H-antigen of the A type RBC?