Flashcards in MCM Final Deck (170)
This protein sorting pathway is used for proteins destined for cytosol, mitochondria, nucleus, and peroxisomes
This protein sorting pathway synthesizes proteins destined for the ER, lysosomes, plasma membranes, and for secretion
What is the protein sorting signal that, when present, destines proteins for the cytoplasm
> Trick question. No sorting signal for this destination.
What is the protein sorting signal that, when present, destines proteins for the mitochondria
A hydrophobic alpha helix
What is the protein sorting signal that, when present, destines proteins for the nucleus
Terminal Lys/Arg repeats
What is the protein sorting signal that, when present, destines proteins for the lysosome
What is the protein sorting signal that, when present, destines proteins for a secretory vesicle
Trp rich domain (absent of retention motifs too)
What is the protein sorting signal that, when present, destines proteins to stay in the ER
What disease is caused by a defect in the enzyme required to tag proteins with an M6P signal?
I cell disease. Proteins (hydrolases to be specific) that should be sent to the lysosome are instead packaged for export from the cell and this causes release of harmful enzymes into the blood. Yikes.
Proteins sent to the mitochondria are recognized by what mitochondrial membrane transporters?
TIM and TOM
How are unfolded proteins protected in the mitochondria?
Binding to chaperones does the trick (HSP70 specifically)
How do nuclear proteins enter that membrane bound organelle?
Via specific nuclear pores
Large proteins destined for the nucleus require a nuclear localization signal which includes four basic residues. Which amino acids are present here?
Name the segment of a protein synthesized for secreting that binds ER targeting signal and then the ribosome during translation
Signal recognition particle
What is used to tether the ribosome/mRNA/peptide complex together (also causes temporary halt in translation)
Signal recognition particle (SRP)
Where do proteins undergo post-translational modifications?
ER or Golgi
When a protein contains an ER localization signal, that signal binds the SRP which will then bind what on the RER membrane?
SRP receptor protein
What confirmation will small proteins spontaneously assume
What could happen when large proteins fold without the help of chaperones
Aggregation or proteolysis
What is the term for a protein containing a barrel shaped compartment that admits unfolded proteins and catalyzes their folding? Does this require ATP?
Chaperonins, yes it is ATP dependent
What is the post translational process that converts inactive forms to active enzymes
What are the 3 possible post translational protein modifications
Glycosylation, phosphorylation, disulfide bond formation
What post translational modification Occurs on extracellular proteins only
What post translational modification can be either O linked or N linked
What amino acids serve as binding sites for an O linked glycosylation of a protein post translationally
hydroxyl group of Ser or thr
What amino acids serve as binding sites for an N linked glycosylation of a protein post translationally
Amino group of Asn
What type of bond is formed with the addition of a glycosidic post translational modification
Disulfide bonds form between what functional group of cysteine residues?
Formation and reorganization of disulfide bonds occurs where