Flashcards in Protein Synthesis pt. 3 Deck (20)
Does the synthesis of all proteins begin on cytoplasmic ribosomes?
Which types of proteins complete synthesis on ER bound ribosomes?
and Lysosomal proteins
What determines the site of protein localization?
Signal contained in the primary structure of the protein.
What signal targets a protein for the nucleus?
What signal targets a protein for the membrane and/or secretion?
20-30 AA signal sequence with a string of hydrophobic AAs.
What signal targets a protein to the lysosome?
What protein binds to the secretory, membrane, and lysosomal proteins during translation to target them to the rough ER.
SRP. Signal recognition protein.
Where do proteins go as they are synthesized on the rough ER ribosomes?
They are translated INTO the lumen of the ER via a channel called Sec61.
How do membrane-spanning proteins get translated?
Translocated to rough ER to make the bit inside the ER lumen until a stop transfer sequence (about 50% through) is reached causing the remainder of the protein to be translated in the cytosol.
Where does glycosylation of asparagine occur?
What does peptidyl prolyl isomerase do?
Helps fold proline-rich regions
What does protein disulfide isomerase do?
Promotes native conformation of disulfide bonds
What is O-linked glycosylation and where does it happen?
Glycosylation of Ser/Thr residues that occurs in the golgi apparatus
How is M6P added in the cis golgi to target lysosomal proteins?
Mannose + phosphorylated sugar
then subtract sugar
Fabry's disease is caused by a defect in what?
alpha-galactosidase A resulting in misfolded globosides which then accumulate in lysosomes.
Describe the PDH mutation.
Arginine to proline mutation in pyruvate dehydrogenase (PDH) E1alpha subunit causes it not to be imported efficiently into the mitochondria
How small do molecules have to be to enter the nucleus by free diffusion?
Less than 5000 d
What are Nups?
Nucleopyorins. FG nups (Phe-Gly) form the diffusion barrier and bind transport receptors to enter the nucleus. Also form the nuclear basket.
What is the nuclear lamina?
An amorphous stabilizing structure just below the nuclear envelope.