Gated Transport Flashcards
newly synthesized proteins must ____ properly and undergo various ______
fold, modifications
what does it mean when a protein is folded co-translationally?
folded immediately as proteins are synthesized
what is a molten globule?
quick formation of an approximate secondary structure from the almost there state
what are molecular chaperones?
proteins needed to assist in protein folding
what is HSP?
heat shock protein, they help proteins fold and shield hydrophobic patches (can get messed up if exposed to water)
what is HSP60 and HSP70
HSP70 then HSP60
HSP70- associates as a polypeptide emergence?
HSP60- barrel like structure that holds unfolded proteins helps it refold
what happens to proteins that are not properly folded?
try to refold correct but if not gets degraded
how do you know when a protein is properly folded?
does not have hydrophobic patches
what is a proteasomes?
for protein degradation, many copies in cytosol and nucleus, stack of 4 rings, central core where degradation occurs and caps that gate for proteins marked for degradation
what is the polyubiquitin chain?
marks a protein to be degraded, gets recognized by proteasome cap
what is ubiquitination?
putting a ubiquitin onto a protein
what is the E2/E3 complex (ubiquitan ligase)?
puts a ubiquitin onto the bad protein
what is E2 (ubiquitin-conjugated enzyme)?
holds onto ubiquitin thats gonna be put onto protein.
what is E1?
ubiquitin activating enzyme. takes in ubiquitin and interacts with E2 to put it on
whats an additional function of ubiquitin?
DNA repair, endocytosis, histone regulation, regulate protein function
what are prion diseases?
2 ways to fold a protein (good and bad), bad influences the good to change shape and they are resistant to degradation
what are FG repeats?
line nuclear pore complex, unstructured, permeability to large molecules, and act as a docking site for nuclear cargo receptors.
what is the nuclear localization signal?
tag on a protein that says it needs to go in/out of nucleus, has + charged residues from arg and lys, can be located anywhere on protein, binds to nuclear import receptors/ nuclear import adaptor proteins
what is gtp hydrolysis?
GTP turns into GDP, phosphate group leaves
what are g-proteins?
protein that can bind to GTP
describe ran mediated nuclear import/export
- an active G-protein will undergo GTP hydrolysis which turns the GTP into GDP
- the g-protein is now inactive and the GDP will leave
- another GTP will come and attach to the g-protein turning it active again
what is GTPase?
enzymatic activity that hydrolyzes GTP to GDP
what is guanine nucleotide exchange factor?
kicks GDP off of g-protein, only exists in the nucleus. binds to chromatin
nuclear import receptor only binds to ____ not ____
GTP, GDP
describe ran mediated nuclear import with the receptors (hard version >:) )
- nuclear import receptor binds to a protein with nuclear localization signal (cargo) and goes into the nucleus
- nuclear import receptor delivers cargo to nucleus and ran-gtp binds to it
- nuclear import receptor goes back to the cytosol and GTP turns into GDP and nuclear import receptor lets go and starts the process over
nuclear export receptor can only bind to cargo if its also bound with ___
ran-GTP
nuclear export/import receptor can go ____ ____ in nuclear pore complex
both ways idk they dumb
describe ran mediated nuclear export with the receptors (hard version >:) )
- nuclear export receptor goes through nuclear pore complex and binds with ran-gtp and cargo in nucleus
- nuclear export receptor goes to the cytosol where ran-GAP transforms GTP into GDP and it lets go of both ran-GDP and cargo
what is the point of ran-GEF?
makes sure theres another ran-GTP in nucleus
what is the ER signal sequence?
1 or more + charged AA sequence next to 6-12 hydrophobic residues (core)
what is co-translational translocation?
directs new protein to ER membrane as it is being synthesized
what is post-translational translocation?
fully translated when transferred
what are the rough patches on the ER?
ribosomes doing translation
what is signal-recognition particle?
recognize ER signal sequence, temporarily stops translation. binds to SRP-receptor on surface of ER
describe ER translocation
- ribosome binds to SRP causing a pause in translation
- SRP binds to SRP receptor of ER
- SRP and its receptor are released
what does a closed translocator look like?
plug is..plugged in
what does an open translocator look like?
signal peptide binds to it. plug moves and the growing polypeptide chain will go through.
where does translation take place if the protein is needed in the cytosol?
cytosol
what are soluble proteins?
proteins not transmembrane, completely soluble in the lumen of ER, secreted to the outside of cell
what is signal peptidase?
enzyme on ER membrane that cleaves off ER signal peptide
what are transmembrane proteins?
has to work on a membrane has to cross and stay in membrane
what is internal ER signal sequence?
binds to translocator. translation occurs.
what is stop transfer sequence?
hydrophobic region of protein. stops translation
what happens if the + AA are before hydrophobic core?
embedded in end terminus in cytosol?
what happens if the + AA are after hydrophobic core?
embedded in the terminus of ER
what is a multipass transmembrane protein?
mix of start end transfer sequence, protein goes in and out of membrane
will a protein that is going to be secreted have a stop transfer sequence?
its not sticking in membrane. has to go to ER
what proteins wouldn’t go to ER?
cytosolic proteins, histones,
what are post-translational translocation?
complete proteins going in membrane
what is glycosylation?
carbohydrates attached to proteins. begins in ERs and into golgi
what are the 2 ways to link oligosaccharides?
n-linked and o-linked glycosylation. trimming and processing needed. is a timer to see how long the proteins been there
when is retrotranslation apparatus needed?
protein is modified but hasnt progressed. something is wrong with protein and is degraded
what is the process of retrotranslation apparatus
protein translocator recognizes and transfer protein into cytosol. E3 ubiquitin marks for degradation. proteasome degrades misfolded protein
what type of translocation does mitochondria use?
post-translational translocation
post-translational translocation are relatively ______
unfolded
what is TOM complex?
translocator of outer mitochondrial membrane
what is TIM (22/23) complex?
translocator of inner mitochondrial membrane
what is SAM complex?
translocator of outer mitochondrial membrane
what is OXA complex?
translocator of inner mitochondrial membrane. used when proteins go into matrix but are needed for inner membrane
describe how matrix proteins get into mitochondria
mitochondrial translation signal recognized by TOM complex. pushed through TlM complex. signal peptide gets cleaved by signal pepidase.
describe how inner membrane proteins get in mitochondria
mitochondrial translation signal recognized by TOM complex. doesn’t go through TIM. signal peptide cleaved.
what happens when a protein goes through a TOM complex but not TIM?
protein goes into inner membrane space through TOM and chaperones help you fold.