Article Abstract:
A study was conducted to determine the physiological mechanism responsible for the postranslational transportation of proteins across the membrane of the yeast endoplasmic reticulum (ER). Results of experiments with Sacchromyces cerevisiae indicate that BiP, a member of the Hsp70 family resident in the ER lumen, allows the translocation of the secretory protein prepro-L factor across the ER membrane by acting as a molecular ratchet. This BiP capability occurs after interacting with the J domain of the Sec63p component of the Sec complex.
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Article Abstract:
A purified complex of yeast proteins contained a heterotrimeric Sec61p that is similar to the Sec complex found in mammals. It also contained membrane proteins that act as translocational components of the endoplasmic reticulum membrane during protein transport. The complex required the presence of lumenal Kar2p and ATP for effective posttranslational translocation. Unlike the large Sec complex, Sec61p expressed association with membrane-bound ribosomes, showing that the complex is homologous Sec protein found in the mammalian complex.
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Article Abstract:
Previous research has shown that importin-alpha's mediation of nuclear protein import involves binding nuclear localization signals and importin-beta. Approximately 30% of the yeast importin-alpha SRP1p is discovered in the Saccharomyces cerevisiae nuclear cap-binding protein complex. Evidence shows that there is an existing mechanism that ensures that importin-mediated RNA release is a specifically cytoplasmic event.
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