Three proteins of stripped rough microsomes (SRM) from dog pancreas or rat liver, with apparent molecular weights of 35, 56 and 90 kDa (pgp35, pp56, pp90), were phosphorylated in vitro by both ($ tau$-32P) GTP and ($ tau$-32P) ATP. Another SRM protein of 15 kDa (pp15) was phosphorylated in vitro only by ($ tau$-32P) GTP. Comparison of the in vitro phosphorylation profile of SRM to those of other well defined subcellular fractions, i.e., plasma membranes, Golgi apparatus, lysosomes, endosomes, mitochondria and smooth microsomes, showed the four major GTP phosphorylated proteins were restricted to the endoplasmic reticulum (ER). Further characterization of these proteins showed them to be phosphorylated on serine residues at the cis face of SRM and to be integral membrane proteins. The 35 kDa protein was glycosylated, with 2 N-linked oligosaccharide sidechains, therefore possessing a luminal domain. Competition and inhibition studies showed that GTP and ATP phosphorylation of the proteins were distinct. Regulation of GTP specific phosphorylation was by adenosine nucleoside. Purification of the 35 and 90 kDa phosphoproteins was achieved, along with another nonphosphorylated glycoprotein of 25 kDa, as a phosphoglycoprotein complex which elutes from Sephacryl S300 chromatography at an apparent molecular weight of about 400,000. Partial Sequence Receptor (Weidmann et al, (1987) Nature 328: 830-833), suggesting that this phosphoglycoprotein complex may form part of the translocation apparatus of the rough ER. These results suggest a role for phosphorylation of ER membrane proteins in the process of translocation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.74286 |
| Date | January 1989 |
| Creators | Rindress, Donna E. (Donna Ellen) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Anatomy.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001069298, proquestno: AAINN63499, Theses scanned by UMI/ProQuest. |
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