Abstract
Tail-anchored (TA) proteins provide an ideal model for studying post-translational integration at the endoplasmic reticulum (ER) of eukaryotes. There are multiple pathways for delivering TA proteins from the cytosol to the ER membrane yet, whereas an ATP-dependent route predominates, none of the cytosolic components involved had been identified. In this study we have directly addressed this issue and identify novel interactions between a model TA protein and the two cytosolic chaperones Hsp40 and Hsc70. To investigate their function, we have reconstituted the membrane integration of TA proteins using purified components. Remarkably, we find that a combination of Hsc70 and Hsp40 can completely substitute for the ATP-dependent factors present in cytosol. On the basis of this in vitro analysis, we conclude that this chaperone pair can efficiently facilitate the ATP-dependent integration of TA proteins.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / metabolism
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Amino Acid Sequence
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Animals
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Biological Transport, Active / physiology
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Cytosol / metabolism
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Endoplasmic Reticulum / metabolism*
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Endoplasmic Reticulum / ultrastructure
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HSC70 Heat-Shock Proteins / genetics
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HSC70 Heat-Shock Proteins / metabolism*
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HSP40 Heat-Shock Proteins / genetics
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HSP40 Heat-Shock Proteins / metabolism*
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Humans
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Membrane Proteins / chemistry
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Molecular Chaperones / genetics
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Molecular Chaperones / metabolism*
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Molecular Sequence Data
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Protein Processing, Post-Translational / physiology*
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Protein Structure, Tertiary / physiology
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Protein Transport / physiology
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RNA, Messenger / metabolism
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Rats
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SEC Translocation Channels
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Vesicle-Associated Membrane Protein 2 / chemistry
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Vesicle-Associated Membrane Protein 2 / genetics
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Vesicle-Associated Membrane Protein 2 / metabolism
Substances
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HSC70 Heat-Shock Proteins
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HSP40 Heat-Shock Proteins
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Hspa8 protein, rat
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Membrane Proteins
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Molecular Chaperones
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RNA, Messenger
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SEC Translocation Channels
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SEC61B protein, human
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VAMP2 protein, human
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Vesicle-Associated Membrane Protein 2
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Adenosine Triphosphate