A protein-conducting channel in the endoplasmic reticulum
1Laboratory of Cell Biology, Howard Hughes Medical Institute, Rockefeller University, New York, New York 10021-6399.
Cell
|May 3, 1991
Summary
Researchers used electrophysiology to demonstrate a protein-conducting channel in the endoplasmic reticulum membrane. Ribosomes attached to the channel keep it open, and their removal by puromycin or salt changes conductance.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biophysics
Background:
- The endoplasmic reticulum (ER) membrane facilitates protein translocation.
- Protein-conducting channels are crucial for protein insertion and folding.
- Understanding channel dynamics is key to ER function.
Purpose of the Study:
- To demonstrate the existence of a protein-conducting channel in the ER membrane.
- To investigate the role of ribosomes in channel gating.
- To elucidate the mechanism of channel opening and closing.
Main Methods:
- Electrophysiological techniques were employed using planar lipid bilayers.
- Pancreatic rough microsome (RM) vesicles were fused to lipid bilayers.
- Puromycin was used to induce clearance of nascent protein chains.
Main Results:
- A significant increase in membrane conductance was observed upon puromycin addition.
- Single channels with a conductance of 220 pS were identified at low puromycin concentrations.
- Channel closure occurred at higher salt concentrations, correlating with ribosome detachment.
Conclusions:
- The study provides electrophysiological evidence for ER protein-conducting channels.
- Attached ribosomes are essential for maintaining the open state of the channel.
- A model for the protein-conducting channel's gating cycle is proposed.
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