Article Abstract:
The synthesis of membrane proteins has been determined as a concerted process of translation, translocation and integration. The integration of a transmembrane segment (TMS) in the endoplasmic reticulum (ER) is based on a cell recognition process. TMS undergoes integration into the phospholipid bilayer only after the entire process of synthesis has occurred. The release of the proteins from the ribosome also precedes the integration process. The detection of TMS from the urea also suggests that the translocated protein is not present in the lipid bilayer core.
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Article Abstract:
Purified mammalian and yeast Sec61p complexes in detergent form cylindrical oligomers with a diameter of approximately 85 angstroms and a central pore of approximately 20 angstroms. These cylindrical oligomers are proposed to represent protein-conducting channels of the endoplasmic reticulum membrane. Through electron microscopy, it was found that each oligomer contains 3-4 heterotrimers. The Sec61p complex's association with ribosomes or the Sec62/63p complex stimulates its oligomer formation.
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Article Abstract:
The coupling mechanism between the endoplasmic reticulum (ER) calcium anion stores and the 'store-operated' calcium anion entry channels of the plasma membrane (PM) was studied through a new combination of cytoskeletal modifications. The results indicate that the observed coupling is mediated by a physical 'secretion-like' mechanism. The same mechanism is determined to be induced by close but reversible interactions between the PM and the ER.
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