The Role of Molecular Chaperones in Protein Transport into the Endoplasmic Reticulum [and Discussion]

In eukaryotic cells export of the vast majority of newly synthesized secretory proteins is initiated at the level of the membrane of the endoplasmic reticulum (microsomal membrane). The precursors of secretory proteins are not transported across the microsomal membrane in their native state. Typical...

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Bibliographic Details
Published in:Philosophical transactions of the Royal Society of London. Series B. Biological sciences 1993-03, Vol.339 (1289), p.335-341
Main Authors: Dierks, Thomas, Klappa, Peter, Wiech, Hans, Zimmermann, Richard, Lindquist, S., Welch, W. J., Viitanen, P., Lorimer, G. H.
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Animals
Biological Transport
Chaperonins
Endoplasmic reticulum
Endoplasmic Reticulum - metabolism
Heat shock proteins
Hydrolysis
Mammals
Microsomes
Microsomes - metabolism
Models, Biological
Molecular chaperones
Protein Folding
Protein precursors
Protein transport
Proteins - metabolism
Receptors
Reticulocytes
Yeasts
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Summary:In eukaryotic cells export of the vast majority of newly synthesized secretory proteins is initiated at the level of the membrane of the endoplasmic reticulum (microsomal membrane). The precursors of secretory proteins are not transported across the microsomal membrane in their native state. Typically, signal peptides in the precursor proteins are involved in preserving the transport-competent state. Furthermore, there are two alternatively acting mechanisms involved in preserving transport competence in the cytosol. The first mechanism involves two ribonucleoparticles (ribosome and signal recognition particle) and their receptors on the microsomal surface and requires the hydrolysis of GTP. The second mechanism does not involve ribonucleoparticles and their receptors but depends on the hydrolysis of ATP and on cis-acting molecular chaperones, such as heat shock cognate protein 70 (hsc 70). In both mechanisms a translocase in the microsomal membrane mediates protein translocation. This translocase includes a signal peptide receptor on the cis-side of the microsomal membrane and a component that also depends on the hydrolysis of ATP. At least in certain cases, an additional nucleoside triphosphate-requiring step is involved which is related to the trans-acting molecular chaperone BiP.
ISSN:0962-8436
1471-2970
DOI:10.1098/rstb.1993.0032