Topic 4, Lecture 2 Flashcards
Describe the anatomy of the mitochondria.
Outer membrane, intermembrane space, inner membrane, matrix
Describe the inner mitochondrial membrane
The inner membrane has cristae (folds) to allow for the electron transport chain (ETC). Because of the ETC, the inner membrane is about 75-80% proteins.
Describe the outer mitochondrial membrane.
The outer membrane is not attached to the inner membrane like the nucleus. The outer membrane is composed of about 50% proteins and 50% lipids.
Describe the mitochondrial matrix.
Hardest space to get to because we have to cross all of the other membranes.
Describe mitochondrial “pores”.
Not really pores but channels. Made up of alpha helices and beta sheets.
Describe the mitochondrial signal sequence.
The mitochondrial signal sequence is on the amino terminus, its long, no acidic amino acids, gets cleaved by signal peptidase.
Describe the relation between alpha helices and the mitochondrial signal sequence.
Alpha helices make a full turn every 3.6 amino acids. There is a basic amino acid about every 3.6 amino acids on the mitochondrial signaling sequence. This causes the sequence to be amphipathic.
Amphipathic
One side polar and one side nonpolar
Is mitochondrial protein transport post- or co-translational?
Post-translational
Do proteins enter the mitochondria folded or unfolded?
Unfolded
How do mitochondrial proteins enter the mitochondria unfolded if the process is post-translational?
Cytosolic Hsp70 is bound to the protein to prevent folding.
Describe the anatomy of the TOM complex.
TOM has a translocation channel and receptors
What is the name of the location of where TIM23 moves up to touch the TOM complex?
Contact Site
Does the mitochondrial signaling sequence get cleaved? If so, how?
Yes, signal peptidase
Does the mitochondrial signaling sequence get cleaved? If so, how?
Yes, signal peptidase
Describe the function of Hsp70.
Bind and stabilize unfolded or partly folded proteins to prevent aggregation, acts co-translationally
What is the energy source for mitochondrial protein transport?
ATP hydrolysis of cytosolic and mitochondrial Hsp70 and the Proton Motive Force
Why do we need to hydrolyze ATP in the mitochondrial matrix?
To power translocation, to keep the protein from going back out TIM23
When does the proton motive force occur?
During cellular respiration
OIL RIG
Oxidation is lose, reduction is gain
Describe MIA40
Mia40 is reduced and oxidizes the imported protein. When this happens, the sulfur atoms on the cysteines are available for disulfide bonding.
Why is disulfide bonding important for proteins in the intermembrane space?
The disulfide bonds make the protein too big to get back out through the TOM complex but still small enough to get through TIM23
Oxidant
Something that removes and/or accepts electrons
Signal Anchor
Some mitochondrial proteins have an extra sequence to decide which path they take, transmembrane domain/segment
