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Eur J Biochem. 2000 Dec;267(24):6989-95.

Identification of low-density Triton X-100-insoluble plasma membrane microdomains in higher plants.

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Institut für Allgemeine Botanik, Lehrstuhl Pflanzenphysiologie, Jena, Germany; Institut für Ultrastrukturforschung des Klinikums der Friedrich Schiller Universität Jena, Germany.


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.

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