title: Z-membranes: artificial organelles for overexpressing recombinant integral membrane proteins.
abstract: We have expressed a fusion protein formed between the avian infectious bronchitis virus M protein and the bacterial enzyme beta-glucuronidase in transgenic tobacco cells. Electron microscope images of such cells demonstrate that overexpression of this fusion protein gives rise to a type of endoplasmic reticulum membrane domain in which adjacent membranes become zippered together apparently as a consequence of the oligomerizing action of beta-glucuronidase. These zippered (Z-) membranes lack markers of the endoplasmic reticulum (NADH cytochrome c reductase and ribosomes) and accumulate in the cells in the form of multilayered scroll-like structures (up to 2 micrometers in diameter; 20-50 per cell) without affecting plant growth. The discovery of Z-membranes has broad implications for biology and biotechnology in that they provide a means for accumulating large quantities of recombinant membrane proteins within discrete domains of native membranes.
authors.affiliation: Department of Plant Sciences, University of Arizona, Tucson, 85721, USA.
authors.forename: F C
authors.initials: FC
authors.lastname: Gong
authors.forename: T H
authors.initials: TH
authors.lastname: Giddings
authors.forename: J B
authors.initials: JB
authors.lastname: Meehl
authors.forename: L A
authors.initials: LA
authors.lastname: Staehelin
authors.forename: D W
authors.initials: DW
authors.lastname: Galbraith
mesh_terms: D001483:Base Sequence; D002474:Cell-Free System; D017931:DNA Primers / Q000737:chemistry; D019084:Fluorescent Antibody Technique, Indirect; D005814:Genes, Viral; D005966:Glucuronidase / Q000737:chemistry*; D001351:Infectious bronchitis virus / Q000235:genetics; D007425:Intracellular Membranes / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000737:chemistry*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D015388:Organelles / Q000648:ultrastructure*; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011994:Recombinant Proteins / Q000737:chemistry; D014026:Nicotiana; D014763:Viral Matrix Proteins / Q000235:genetics; D015678:Viral Structural Proteins / Q000235:genetics
chemical_list: D017931:DNA Primers; D008565:Membrane Proteins; D011994:Recombinant Proteins; D014763:Viral Matrix Proteins; D015678:Viral Structural Proteins; D005966:Glucuronidase