Unit 4 Flashcards
What is the function of Ran GTPase in nuclear transport?
Regulates the binding and release of cargo proteins during import/export through nuclear pores.
What vesicle type moves proteins from the ER to the Golgi?
COPII vesicles.
What happens to proteins with a KDEL sequence?
They are retrieved back to the ER from the Golgi via COPI vesicles.
What types of bonds stabilize protein structures in the ER?
Disulfide bonds.
What is the role of the Unfolded Protein Response (UPR)?
Helps reduce ER stress by halting protein translation, degrading misfolded proteins, and increasing chaperone production.
What is the difference between one-pass and multi-pass membrane proteins?
One-pass proteins use a single stop-transfer sequence, while multi-pass proteins have multiple start and stop-transfer sequences.
How does glycosylation affect proteins?
It stabilizes proteins, aids in cell-cell communication, and determines protein destination.
What is autophagy?
A cellular process for degrading damaged organelles or proteins.
What triggers regulated exocytosis?
External signals, such as hormones or neurotransmitters.
What is the purpose of proteasomes?
They degrade misfolded or damaged proteins tagged with ubiquitin.
what is protein sorting
the process by which proteins are directed to specific locations within or outside the cell, this is guided by signal sequences
What are signal sequences
short stretches of AA that direct proteins to their appropriate cellular components
Free Ribosomes
Free ribosomes are located in the cytosol, they synthesize proteins that function in the cytosol, mitochondria, chloroplasts, nucleus, and peroxisomes
what are polyribosomes
cluster of free ribosomes translating the same mRNA simultaneously
Membrane Bound Ribosomes
ribosomes that are embedded in the ER, they synthesize proteins that are destined for secretion, incorporation into the plasma membrane or lysosomes
what proteins are made in membrane bound ribosomes
transmembrane, integral membrane proteins, soluble proteins for secretion, soluble proteins that will remain inside the ER, Golgi, or lysosomes
proteins from membrane bound ribosomes travel though vesicles in the order of
vesicles to golgi to surface (proteins in plasma membrane) or to be secreted
or
vesicles to golgi to lysosomes
Nuclear Transport of proteins
proteins that contain nuclear localization signals (NLS) are recognized by nuclear import receptors, the nuclear envelope allows transport through nuclear pore complexes
Role of RAN in Protein transport
Ran is a GTPase that provides energy for the import and export of proteins across the nuclear envelope by facilitating cargo binding and release though nuclear pores
Steps of RAN usage (steps of how proteins enter the nucleus)
must have NLS, the NLS signal is recognized by receptor in cytoplasm called importin, the receptor picks up the nuclear protein in the cytosol and directs it to the nuclear pore, importin grabs onto the repeated AA sequences at the rim of the pore making a passage way pulling the proteins though
once inside the nuclear envelope, the protein encounters RAN, RAN GTP binds to receptor causing it to release cargo, importin carrying the GTP is transported back through pore and hydrolyzed back to GDP to start process over
mitochondrial transport
proteins containing targeting signals that direct them to the mitochondrial surface, where they are translocated across the membrane
peroxisomal transport
proteins are imported post translationally guided by peroxisomal targeting signals
endomembrane system
group of organelles including the ER, Golgi, lysosomes, and vesicles involved in transport and processing of all proteins destined for secretion or lysosomal use
transport of proteins to the endomembranous system
proteins moving from ER onward through endomembrane system are transported though transport vesicles which become loaded w cargo proteins they pinch off from one organelle and travel to the next
protiens with ER signal sequences are directed to the ER where they begin the secretory pathway
