Signal Sequence Processing in Rough Microsomes (*)
- Frank Lyko(1),
- Bruno Martoglio(1)(§),
- Berit Jungnickel(2),
- Tom A. Rapoport(2) and
- Bernhard Dobberstein(1)
- From the (1)ZMBH, Universität Heidelberg, Postfach 106249, 69052 Heidelberg, Germany and the
- (2) Max-Delbrück-Zentrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 10115 Berlin-Buch, Germany
- §To whom correspondence should be addressed. Tel.: 49-6221-568299; Fax: 49-6221-565892.
Abstract
Secretory proteins are synthesized with a signal sequence that is usually cleaved from the nascent protein during the translocation of the polypeptide chain into the lumen of the endoplasmic reticulum. To determine the fate of a cleaved signal sequence, we used a synchronized in vitro translocation system. We found that the cleaved signal peptide of preprolactin is further processed close to its COOH terminus. The resulting fragment accumulated in the microsomal fraction and with time was released into the cytosol. Signal sequence cleavage and processing could be reproduced with reconstituted vesicles containing Sec61, signal recognition particle receptor, and signal peptidase complex.
Footnotes
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↵* This work was supported by the Deutsche Forschungsgemeinschaft (SFB 352) and the Human Frontier Science Program Organization. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- SRP
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signal recognition particle
- ER
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endoplasmic reticulum
- SPC
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signal peptidase complex
- PPL
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preprolactin
- PL
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prolactin
- PSP
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processed signal peptide
- SP
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signal peptide
- MHC
-
major histocompatibility complex
- TAP
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transporter associated with antigen presentation.
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↵2E. Hartmann, S. Prehn, K.-U. Kalies, and T. A. Rapoport, unpublished results.
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- Received February 22, 1995.
- Revision received June 19, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
