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25 Cards in this Set
- Front
- Back
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Which organelles are competent to take up newly synthesized proteins? (5)
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ER, Mitochondria, Chloroplast, Peroxisome, Nucleus
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Three compartments contain their signal within the N-terminal. (3)
What else is special about these signals? |
ER, Mitochondria, Chloroplast
Signals are cleaved. |
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Nature of ER signal
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6-12 hydrophobic a.a.
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Nature of Mitochondria signal
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3-5 non-consecutive Arg/Lys
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Nature of Chloroplast signal
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rich in Serine and Threonine
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Where is the location of the signal for peroxisomal proteins?
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C-terminal
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Nature of Peroxisome signal
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Ser-Lys-Leu
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Where is the location of the signal for Nucleosomal proteins?
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Internal
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Nature of Nucleosomal signal
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basic a.a.
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Is the signal sequence removed in the peroxisome and the nucleus?
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No.
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Topogenesis refers to:
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Targetting of protein due to a specific sequence
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Three types of sequences:
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Signal sequence
Membrane anchor sequence Sorting sequence |
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What is a sorting sequence?
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Target to a specific membrane layer
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Signal sequence
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Target to a specific organelle.
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Verification of existence of signal sequence: (2 methods)
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Delete sequence and observe membrane
Place sequence onto a cytoplasmic protein and observe where the protein ends up. |
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Conformation of protein before integration occurs: (2 methods)
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Intrinsically (nascent chain synthesis) - co-translational
Chaperones - post-translational |
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Cytosolic movement towards membranes: (how?)
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Driven by diffusion
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Recognition of protein onto proper organelle mediated by what type of surface structure?
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Specific organelle surface receptor.
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Does the receptor have high affinity for the membrane protein?
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If there was high affinity, then the protein would be stuck on the receptor.
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Channel proteins must maintain aqueous environment.
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Metabolites cannot leak through, thus channels must be dynamic and gate against leakage of small molecules.
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Where does the energy come from protein translocation? (4)
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1)- ATP + GTP hydrolysis
2)- Electrochemical/Proton gradient 3)- Chaperones (ATP-dependent) 4)- Folding into final protein conformation |
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At which stage, does the protein fold into its final conformation?
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When it has reached the opposite side of the membrane.
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Which cellular location does the s.s. get cleaved?
Why? (two hypothesis) |
Removed on trans side of membrane.
Maintains unidirectionality, S.s. might have kept protein in partial unfolded state. |
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How are proteins inserted into the membrane?
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Coupled to translocation across membrane.
When channel reaches a membrane anchor sequence, it will insert into membrane. |
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What is the structure of a transmembrane domain in a protein?
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Helix of 20 hydrophobic amino acids.
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