Identification of low-density Triton X-100-insoluble plasma membrane microdomains in higher plants.
Low density Triton X-100-insoluble plasma membrane microdomains can be isolated from different mammalian cell types and are proposed to be involved in membrane trafficking, cell morphogenesis and signal transduction. Heterotrimeric G-proteins and their receptors are often associated with such domains, suggesting that these structures are involved in G-protein-coupled signaling. Here we report that detergent-insoluble plasma membrane microdomains also exist in higher plants and contain about 15% of membrane-bound heterotrimeric G-protein beta-subunit (Gbeta). Plasma membrane microdomains were isolated from tobacco leaves. They have low buoyant density relative to the surrounding plasma membrane, and are insoluble in Triton X-100 at 4 degrees C. Detergent-insoluble vesicles were examined by freeze-fracture electron microscopy. They have sizes in the range 100-400 nm, and often contain aggregated protein complexes. The majority of plasma membrane proteins cannot be detected in the Triton X-100-insoluble fraction, while few polypeptides are highly enriched. We identified six proteins with molecular masses of 22, 28, 35, 60, 67 and 94 kDa in detergent-insoluble fractions that are glycosylphosphatidylinositol (GPI)-anchored.
Peskan
T
T
Institut für Allgemeine Botanik, Lehrstuhl Pflanzenphysiologie, Jena, Germany; Institut für Ultrastrukturforschung des Klinikums der Friedrich Schiller Universität Jena, Germany.
Westermann
M
M
Oelmüller
R
R
D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D005614:Freeze Fracturing; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D017830:Octoxynol / Q000494:pharmacology*; D010947:Plants, Toxic; D014026:Nicotiana / Q000378:metabolism / Q000648:ultrastructure*
D017261:Glycosylphosphatidylinositols; D017830:Octoxynol