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. 1988 Apr 1;106(4):1043–1048. doi: 10.1083/jcb.106.4.1043

Full-length prepro-alpha-factor can be translocated across the mammalian microsomal membrane only if translation has not terminated

PMCID: PMC2115022  PMID: 2834400

Abstract

We have previously shown that fully synthesized prepro-alpha-factor (pp alpha F), the precursor for the yeast pheromone alpha-factor, can be translocated posttranslationally across yeast rough microsomal (RM) membranes from a soluble, ribosome-free pool. We show here that this is not the case for translocation of pp alpha F across mammalian RM. Rather we found that a small amount of translocation of full-length pp alpha F is observed, but is solely due to polypeptide chains that were still ribosome bound and covalently attached to tRNA, i.e., not terminated. In addition, both signal recognition particle (SRP) and SRP receptor are required, i.e., the same targeting machinery that is normally responsible for the coupling between protein synthesis and translocation. Thus, the molecular requirements for targeting are distinct from posttranslational translocation across yeast RM. As termination is generally regarded as part of translation, the translocation of full-length pp alpha F across mammalian RM does not occur "posttranslationally," albeit independent of elongation. Most other proteins for which posttranslational translocation across mammalian RM was previously claimed fall into the same category in that ribosome attachment as peptidyl-tRNA is required. To clearly separate these two distinct processes, we suggest that the term posttranslational be reserved for those processes that occur in the complete absence of the translational machinery. We propose the term "ribosome-coupled translocation" for the events described here.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Blobel G., Dobberstein B. Transfer of proteins across membranes. II. Reconstitution of functional rough microsomes from heterologous components. J Cell Biol. 1975 Dec;67(3):852–862. doi: 10.1083/jcb.67.3.852. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Caulfield M. P., Duong L. T., Rosenblatt M. Demonstration of post-translational secretion of human placental lactogen by a mammalian in vitro translation system. J Biol Chem. 1986 Aug 25;261(24):10953–10956. [PubMed] [Google Scholar]
  3. Chao C. C., Bird P., Gething M. J., Sambrook J. Posttranslational translocation of influenza virus hemagglutinin across microsomal membranes. Mol Cell Biol. 1987 Oct;7(10):3842–3845. doi: 10.1128/mcb.7.10.3842. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Connolly T., Gilmore R. Formation of a functional ribosome-membrane junction during translocation requires the participation of a GTP-binding protein. J Cell Biol. 1986 Dec;103(6 Pt 1):2253–2261. doi: 10.1083/jcb.103.6.2253. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Erickson A. H., Blobel G. Cell-free translation of messenger RNA in a wheat germ system. Methods Enzymol. 1983;96:38–50. doi: 10.1016/s0076-6879(83)96007-x. [DOI] [PubMed] [Google Scholar]
  6. Gilmore R., Blobel G. Translocation of secretory proteins across the microsomal membrane occurs through an environment accessible to aqueous perturbants. Cell. 1985 Sep;42(2):497–505. doi: 10.1016/0092-8674(85)90107-2. [DOI] [PubMed] [Google Scholar]
  7. Gilmore R., Blobel G., Walter P. Protein translocation across the endoplasmic reticulum. I. Detection in the microsomal membrane of a receptor for the signal recognition particle. J Cell Biol. 1982 Nov;95(2 Pt 1):463–469. doi: 10.1083/jcb.95.2.463. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Gilmore R., Walter P., Blobel G. Protein translocation across the endoplasmic reticulum. II. Isolation and characterization of the signal recognition particle receptor. J Cell Biol. 1982 Nov;95(2 Pt 1):470–477. doi: 10.1083/jcb.95.2.470. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Hansen W., Garcia P. D., Walter P. In vitro protein translocation across the yeast endoplasmic reticulum: ATP-dependent posttranslational translocation of the prepro-alpha-factor. Cell. 1986 May 9;45(3):397–406. doi: 10.1016/0092-8674(86)90325-9. [DOI] [PubMed] [Google Scholar]
  10. Hobden A. N., Cundliffe E. The mode of action of alpha sarcin and a novel assay of the puromycin reaction. Biochem J. 1978 Jan 15;170(1):57–61. doi: 10.1042/bj1700057. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Krieg U. C., Walter P., Johnson A. E. Photocrosslinking of the signal sequence of nascent preprolactin to the 54-kilodalton polypeptide of the signal recognition particle. Proc Natl Acad Sci U S A. 1986 Nov;83(22):8604–8608. doi: 10.1073/pnas.83.22.8604. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Kurzchalia T. V., Wiedmann M., Girshovich A. S., Bochkareva E. S., Bielka H., Rapoport T. A. The signal sequence of nascent preprolactin interacts with the 54K polypeptide of the signal recognition particle. Nature. 1986 Apr 17;320(6063):634–636. doi: 10.1038/320634a0. [DOI] [PubMed] [Google Scholar]
  13. Meyer D. I., Krause E., Dobberstein B. Secretory protein translocation across membranes-the role of the "docking protein'. Nature. 1982 Jun 24;297(5868):647–650. doi: 10.1038/297647a0. [DOI] [PubMed] [Google Scholar]
  14. Mueckler M., Lodish H. F. Post-translational insertion of a fragment of the glucose transporter into microsomes requires phosphoanhydride bond cleavage. Nature. 1986 Aug 7;322(6079):549–552. doi: 10.1038/322549a0. [DOI] [PubMed] [Google Scholar]
  15. Mueckler M., Lodish H. F. The human glucose transporter can insert posttranslationally into microsomes. Cell. 1986 Feb 28;44(4):629–637. doi: 10.1016/0092-8674(86)90272-2. [DOI] [PubMed] [Google Scholar]
  16. Palade G. Intracellular aspects of the process of protein synthesis. Science. 1975 Aug 1;189(4200):347–358. doi: 10.1126/science.1096303. [DOI] [PubMed] [Google Scholar]
  17. Perara E., Rothman R. E., Lingappa V. R. Uncoupling translocation from translation: implications for transport of proteins across membranes. Science. 1986 Apr 18;232(4748):348–352. doi: 10.1126/science.3961485. [DOI] [PubMed] [Google Scholar]
  18. Rothblatt J. A., Meyer D. I. Secretion in yeast: translocation and glycosylation of prepro-alpha-factor in vitro can occur via an ATP-dependent post-translational mechanism. EMBO J. 1986 May;5(5):1031–1036. doi: 10.1002/j.1460-2075.1986.tb04318.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Schlenstedt G., Zimmermann R. Import of frog prepropeptide GLa into microsomes requires ATP but does not involve docking protein or ribosomes. EMBO J. 1987 Mar;6(3):699–703. doi: 10.1002/j.1460-2075.1987.tb04810.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Siegel V., Walter P. Elongation arrest is not a prerequisite for secretory protein translocation across the microsomal membrane. J Cell Biol. 1985 Jun;100(6):1913–1921. doi: 10.1083/jcb.100.6.1913. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Tajima S., Lauffer L., Rath V. L., Walter P. The signal recognition particle receptor is a complex that contains two distinct polypeptide chains. J Cell Biol. 1986 Oct;103(4):1167–1178. doi: 10.1083/jcb.103.4.1167. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Walter P., Blobel G. Preparation of microsomal membranes for cotranslational protein translocation. Methods Enzymol. 1983;96:84–93. doi: 10.1016/s0076-6879(83)96010-x. [DOI] [PubMed] [Google Scholar]
  23. Walter P., Blobel G. Purification of a membrane-associated protein complex required for protein translocation across the endoplasmic reticulum. Proc Natl Acad Sci U S A. 1980 Dec;77(12):7112–7116. doi: 10.1073/pnas.77.12.7112. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Walter P., Blobel G. Signal recognition particle: a ribonucleoprotein required for cotranslational translocation of proteins, isolation and properties. Methods Enzymol. 1983;96:682–691. doi: 10.1016/s0076-6879(83)96057-3. [DOI] [PubMed] [Google Scholar]
  25. Walter P., Blobel G. Translocation of proteins across the endoplasmic reticulum III. Signal recognition protein (SRP) causes signal sequence-dependent and site-specific arrest of chain elongation that is released by microsomal membranes. J Cell Biol. 1981 Nov;91(2 Pt 1):557–561. doi: 10.1083/jcb.91.2.557. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Walter P., Ibrahimi I., Blobel G. Translocation of proteins across the endoplasmic reticulum. I. Signal recognition protein (SRP) binds to in-vitro-assembled polysomes synthesizing secretory protein. J Cell Biol. 1981 Nov;91(2 Pt 1):545–550. doi: 10.1083/jcb.91.2.545. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Walter P. Signal recognition. Two receptors act sequentially. 1987 Aug 27-Sep 2Nature. 328(6133):763–764. doi: 10.1038/328763a0. [DOI] [PubMed] [Google Scholar]
  28. Waters M. G., Blobel G. Secretory protein translocation in a yeast cell-free system can occur posttranslationally and requires ATP hydrolysis. J Cell Biol. 1986 May;102(5):1543–1550. doi: 10.1083/jcb.102.5.1543. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Watts C., Wickner W., Zimmermann R. M13 procoat and a pre-immunoglobulin share processing specificity but use different membrane receptor mechanisms. Proc Natl Acad Sci U S A. 1983 May;80(10):2809–2813. doi: 10.1073/pnas.80.10.2809. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Wiedmann M., Kurzchalia T. V., Hartmann E., Rapoport T. A. A signal sequence receptor in the endoplasmic reticulum membrane. 1987 Aug 27-Sep 2Nature. 328(6133):830–833. doi: 10.1038/328830a0. [DOI] [PubMed] [Google Scholar]
  31. Zimmermann R., Mollay C. Import of honeybee prepromelittin into the endoplasmic reticulum. Requirements for membrane insertion, processing, and sequestration. J Biol Chem. 1986 Sep 25;261(27):12889–12895. [PubMed] [Google Scholar]

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