Protein Sorting I Flashcards
How does transport between nucleus and cytosol work?
Gated Transport.
Through nuclear pore complexes
It also allows for active transport and free diffusion
What type of transport happens between the cytosol and organelle membranes?
Transmembrane Transport
Uses protein translocators that directly transport specific proteins.
What type of membrane-enclosed transport intermediates move proteins between the various compartments via vesicles?
Vesicular transport
What removes a signal sequence once the protein arrives at the destination?
signal peptidases
Signal sequences are both:
necessary and sufficient for protein targeting
Physical properties of the sequence is more important than
the actual sequence.
What recognizes the signal?
complementary receptors
What is the zipcode for the nucleus?
Lys-Lys-Lys-Arg-Lys
What is the zipcode to leave the nucleus
Met-x-x-Leu-x-x-x-Leu-x-x-x-Phe
What is the zipcode to get into the mitochondria?
N-Term-x-x-x-x-ARG-x-x-x-x-Arg-x-x-x-Arg-x-x Lys-x-x-x-Arg-x-x-xArg-x-x-x
scattered integrated positive charge
Zipcode for getting in to the ER:
N-term-x-x-x-x-x-x-xLeu-leu-leu-val-gly-ile=leu=phe=prp=ala-x-x-x-x
All positively charged aa, and one negatively charged
Zipcode to return to the ER
-Lys-Asp-Glu-Leu
What are the proteins that are needed from the cytosol in the nucleus?
histones, dna, rna polymerases, topoisomerase, gene regulatory proteins.
What proteins/molecules are made in the nucleus and sent to the cytosol?
tRNA and mRNA
What are the 30 different proteins of the nuclear envelope called?
NUCLEOPORINS
What is the geometric shape of the nuclear pores?
octagonal symmetry with one or more aqueous pores.
Going through the nuclear pore: SMALL MOLECULES… How?
Passive diffusion and facilitated transport
Transport into the nuclear pore complex is facilitated by binding of particles to :
fibrils… extending from the NPC
What is an NLS?
it’s a zipcode or sorting signal for the protein to go to the nucleus
What is the physical property of the NLS?
Positively charges Lys and Arg (They need to be right next to each other, no interruptions)
Where are the LYS and ARG on the protein for the NLS?
different sites on the protein, forms loops or patches on the surface
The NLS is recognized by what?
NIRs: Nuclear Import Receptors
What is an NIR?
soluble cytosolic proteins that bind to the NLS on protein and to the NPC proteins present on fibrils that extend into the cytoplasm.
The Nuclear pore complex has Phenylalanine glycine repeats called:
FG repeats
What do the FG repeats do?
act as a binding site for import receptors.
What are the steps of going through the NPC?
binding
Dissociating
Re-binding
zipcode to get out of the nucleus?
NES: Nuclear export signal, needs complementary export receptor (NER)
NER binds to cargo present in the nucleus and the NPC proteins
Transport out happens the same say: binding, dissociation, rebinding
GAP or GTPase activating protein is found on which side?
cytosol
GEF or Guanine exchange factor is found on which side?
nuclear
what does the GEF do?
it bumps the GDP off RNA and exchanges it for GTP, therefore activates it.
GEF activates.
Ran-GTP gets you out of the nucleus
