Protein Sorting Flashcards
endosymbiosis
- loss of rigid cell wall in ancient anaerobic archaeon facilitates horizontal gene transfers
- digestion of other prokaryotes (archaeal and bacterial) further increases horizontal gene transfers and cell membrane folds in forming primitive nuclear membrane
- aerobic bacterium is engulfed (retains both membranes and its DNA) = mitochondrion
- chloroplasts are created when a photosynthetic bacterium later is engulfed
endosymbiosis
- where did the inner/outer membranes originate
- what is the matrix equivalent to an intact cell
- what do these previous answers mean for carbohydrate metabolism in bacteria
- why do mitochondria contain DNA
- what genes are in the mitochondrial genome
- why is the universal code not used
- why is this not equivalent to any other compartment
- inner- original bacteria; outer- cell that engulfed (primitive eukaryote)
- cytosol
- took place in plasma membrane (outer) in bacteria
- they were original intact cells
- just the important ones necessary to perform functions in the mitochondria; not enough to sustain life
- mitochondria was engulfed before current genetic code was the universal code
- it evolved parallel to the nucleus; mitochondria were world of their own -what happens in one compartment doesn’t have to happen in the other. mutation rates in mitochondria DNA is much greater than nuclear genome
Gated transport:
- facilitator
- compartments bridged
- compartment topology
- membrane crossed
- nuclear pore complex (NPC)
- nucleus/cytosol
- equivalent
- Yes
Transmembrane
- facilitator
- compartments bridged
- compartment topology
- membrane crossed
- translocator proteins
- cytosol –> organelle
- different
- Yes
Vesicular
- facilitator
- compartments bridged
- compartment topology
- membrane crossed
- vesicle
- organelle –> organelle
- equivalent
- No
sorting signals
- located on cargo to be moved direct traffic flow
- signal patch consolidates many scattered sequences (next to each other after protein folding)
- biochemical properties are more important than amino acid identity
- recognized by complementary receptors on targeted organelle
- necessary and sufficient for protein targeting
- may be removed by a signal peptidase after protein reaches final destination
nuclear import signal sequence
rich in K and R
+ charge
located internally
nuclear export signal sequence
amphipathic
located internally
mitochondria import signal sequence
+ charge
located on N-terminus
ER import signal sequence
hydrophobic core
located on N-terminus
ER return signal sequence
KDEL
helps proteins stay in ER or helps to return to ER if escapes
mixed biochemical features
located on C-terminus
nucleus to cytosol uses what signal
nuclear export signal (NES)
cytosol to nucleus uses what signal
nuclear localization signal (NLS)
Nuclear pore complex (NPC) are made up of
nucleoporins (NUPs)
types of nucleoporins (NUPs)
- scaffold: structural, stabilize membrane
- ring: anchor to membrane
- channel: connectors and gates (FG repeats)
- fibrils: neither structural or symmetrical; interact with proteins
nuclear basket
tethers active genes to the NPC
interact with nuclear lamins
regulation of transport
nuclear import
- sorting signal
- amino acids
- location
- recognized by what
- nuclear localization signal (NLS)
- charged amino acids (K, R)
- multiple internal sites
- Nuclear Import Receptors (NIR): cytosolic proteins; ferry cargo into nucleus; also called importins; direct or indirect recognition
nuclear export
- sorting signal
- biochemical property
- location
- recognized by what
- nuclear export signal (NES)
- amphipathic helices
- internal
- nuclear export receptors (NER): nuclear proteins; ferry cargo into cytosol; recycled back to nucleus; also called exportins; recognition must be indirect when cargo is RNA
shuttling
nucleus to cytosol and back
these cargo proteins may have both and NES and NLS
regulation of recognized signal sequence can be by
- phosphorylation
- proteolysis
- inhibitor proteins
importins and exportins are collectively called
karyopherins
when engery is need for nucleus cytosol movement, what type of energy is used
GTP