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To get into the mito, what does the protien have to be?
What helps this?
What then does the polypeptide have to do?
- straight and not folded
- chaperones
- bind to the receptor
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How many chaperones iwll it take to stranighten out the polypeptide
more than one as well as ATP
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Membrane translocation requires energy of __.
protein-motive force
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Relationship in charge of inner and outer face?
- inner face neg. in relation to the posive outer face
- protein ocncentration gradient allows movement intot eh matrix
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What helps the polypeptide reforld?
What gets cleaved off by what?
different chaperonins
the uptake targeting sequence by the mitochondrion processing peptidase
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If its gonna end up in the matrix, what?
Once in amtrix and folded, what?
- it has to go through both membranes and it may be a couple of different channels
- once in the matrix, adn folded, it stays because it can't get back through the channel
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Brief summary of steps of import of polypeptide into matrix of mitochondria?
- 1) atp-dependent protein brinding to the chaperone protien
- 2) binding to receptor
- 3) membrane translocation (requires energy of proton-motive force)
- 4)prevention of aggregation/ premature folding
- 5) catalysis of folding
- 6) cleavage of uptake-targeting sequence
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The Import of a Polypeptide into the matrix of a mitochondrion
The precursor protein, with its __, is synthesized in the __. There it binds to a __ which uses energy released by __ to keep the precursor unfolded. Then, the __ binds to one or more receptors on the outer membrane near a site of contact with the inner membrane.
- N-terminal matrix-targeting sequence
- cytosol
- cytosolic hsp70 chaperone protien
- ATP bydrolysis
- precursor-chaperone-complex
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The Import of a Polypeptide into the matrix of a mitochondrion
The protein is then __ across the outer and inner membranes through a channel lined with several different types of proteins; one of these __ actually forms part of the import channel. This process requries a __ across the inner membrane, which is a combo of a membrane electric potential and a pH gradient.
- translocated
- ISP42
- proton motive force
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The Import of a Polypeptide into the matrix of a mitochondrion
- Translocation occurs at __ at which the inner and outer membranes appear to touch. The newly imported protein binds to the matrix __, which uses the energy of __ to assist import into the matrix and to prevent __ or __. After its release from __, the protein binds to one end of the __.
- rare sites
- matrix chaperone hsp70
- ATP hydrolysis
- aggregation or premature folding
- hsp70
- 14-subunit chaperonin hsp60
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The Import of a Polypeptide into the matrix of a mitochondrion
Apparently, while the precursor is bound to __, energy released by the __ assists it to fold into its final, active ocnfiguation. The uptake-targeting sequence, having served its function, is remvoed by a __. Some imported proteins remain in the matrix space; others insert into the __ or are inserted into the __.
- hsp60
- hydrolysis of ATP
- matrix protease
- inner membrane
- intermembrane space
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Transport of proteins from the cytosol to the mitochondrial intermembrane space
There are two proposed models for this process, both of which utilize, but in different ways, the same __ at their __.
- uptake targeting sequences
- N-termini
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a) In the first, __, two succcessive translocations are required. First, a __ fucntions to target the protein to the __, exactly as if it were a typical mitochondrial matrix protein. The __ is cleaved by the __ and the protein remains __, presumably bound to __. Then, the __ targets the protein to the __ and initiates __ of hte protein across the inner membrane through a __ and intot eh __. In the __, the sequence is cleaved by a specific __ that is related to the ER __, and __ is added, enabling the __ to fold into its mature configuraiton
- conservative sorting
- matrix-targeting sequence
- mitochrondrial matrix
- matrix-targeting sequence
- matrix protease
- unfolded
- matrix hsp70
- intermembrane-space-targeting sequence
- inner membrane
- translocation
- protien lined channel
- intermembrane space x2
- proteasesignal peptidase
- heme
- cytochrome
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In the 2nd, __, model, the __ initiates __ through botth the outer and inner membranes, btu the __ functions as a __: it remains as an anchor in the inner membrane and prevents translocation of the C-terminus of the protein through it. The protein, anchored int eh membrane by the __, apparently causes disassembly of the __, the rest of hte protein moves across theo outer membrane into the intermembrane space, and the protein diffuses, within the __, away from the __. Finally, the __ is cleaved by a specific __, __ is added, and the __ folds into its mature configuration.
- nonconservative
- matrix targeting sequence
- translocation
- hydrophobic intermembrane space targeting sequence
- stop transfer
- intermembraen space targeting sequnece
- translocation channel
- inner membrane
- translocation site
- intermemrbane space targeting sequence
- protease
- heme
- cytochrome
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Brief summary of the nonconservative model?
- 1) binding to hsp70 protein then to receptor protein
- 2) translocation to matrix
- 3) cleavage of matrix-targeting sequence; movement away from translocation complex
- 4) cleavage of intermembrane-space-targeting sequence; addition of heme
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