Protein sorting I Flashcards
the four things that that matter to the cell when it tries to put proteins into a biological membrane
a signal sequence; the receptor for that sequence; the structure of the translocon; the source of energy for transfer
how are proteins transported across membranes to get where they need to go?
okay theres too much for one flashcard
Cystic fibrosis is an example of ____
genetically mutated protein that is then mis-sorted.
what happens in the mitochondria
TCA; electron transport; ATP production
three things that are required to uptake proteins
proton-motive force; ATP; cytosolic chaperones
tim is?
translocon of inner membrane in mitochondria
tom is?
translocon of outer membrane in mitochondria
what is the energy source for protein import to the mitochondrial MATRIX
Hsc70 ATPase outside; Hsc70ATPase inside; proton-motive force
what is the hallmark feature that encodes for protein import into mitochondrial MATRIX
the targeting sequence is at the N-terminus. its an amphipathic alpha helix about 20-50 residues long, has R and K; charged residues on one side, hydrophobic on the other
Translocation of mitochondrial MATRIX proteins is post-translational (t/f)
true. but it is is folded AFTER translocation
what is the receptor for protein transport into the mitochondrial MATRIX
Tom20/22 is import receptor in outer mitochondrial membrane; it is put through the outer membrane through tom 40 (general import pore); the inner membrane pore is Tim23/17 which is associated with tim44
tim44 recruits who and for what?
matrix Hsc70 that helps keep Mr. protein guy unfolded still (this uses ATP energy)
once the polypeptide is threaded into the mitochondrial MATRIX what happens?
the matrix processing protease takes the targeting sequence off. (just like in the ER)
cytochrome oxidase is a protein in the inner mitochondrial membrane for ETC. What would its targeting sequence look like?
matrix targeting sequence, but it also has a hydrophobic stop transfer sequence; it hits that spot and gets happy and stops. otherwise, this is the same as the matrix transport.
What is the targeting sequence for IMM like ATP synthase?
matrix targeting sequence, but it also has an internal Oxa1 that is a machine to help rethread it through
ADP/ATP antiporter is an IMM protein? What is its targeting signal
it DOESNT have the original matrix targeting sequence
if you have an oxa1 then…
it gets into the mitocondria the same way, BUT it has an EXTRA sequence that threads the protein through
a multiple spanning protein (like ADP/ATP antiporter) uses what translocons to get in?
Tom70 to tell Tom40 what to do: get the thing through the outermembrane; needs Tim54 and Tim22 to get it to span multiple times through inner membrane
how do you keep hydrogen peroxide in the peroxisome
it has catalase that breaks it down
what is the targeting sequence for peroxisomal proteins?
three amino acids on the carboxy sequence, and are specific to peroxisomes. called PTS1 which codes “SKL”
what is the receptor for peroxisomal proteins?
Pex 5 recognizes the SKL and docks with Pex 14; Pex5 remains bound during translocation (unlike ER transport)
what translocon is used for peroxisomal proteins?
Pex 10, 2, and 12.
what two things are different about peroxisomal protein transport?
it can be folded!! also the PTS1 targeting seqence is NOT cleaved!!
Zellweger syndrome defect of
Pex3 and/or Pex1
unlike mitochondria, peroxisomes can arise ___ from precursor membranes drived from ___ as well as____
de novo; ER; by division of pre-existing organelles
know what zellweger would result in
even though you don’t want to
any protein that is to go outside the cell enters the ____
enoplasmic reticulum
