Exam III: 9

  1. 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
  2. How many chaperones iwll it take to stranighten out the polypeptide
    more than one as well as ATP
  3. Membrane translocation requires energy of __.
    protein-motive force
  4. 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
  5. What helps the polypeptide reforld?

    What gets cleaved off by what?
    different chaperonins

    the uptake targeting sequence by the mitochondrion processing peptidase
  6. 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
  7. 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
  8. 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
  9. 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
  10. 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
  11. 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
  12. 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
  13. 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
  14. 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
  15. 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
Card Set
Exam III: 9