The isolation and characterization of right-side-out plasma membrane vesicles from barley aleurone cells.

Examination of organelle- and membrane-specific processes such as signal transduction necessitates the use of plasma membrane vesicles with cytoplasmic side-in orientation. We are interested in the structural identity and subcellular localization of in vivo [32P]phosphoric acid ([32Pi])-labeled phosphoinositides, including the recently discovered phosphatidyl-scyllo-inositol, for signal transduction studies. In the first part of this investigation, plasma membrane vesicles from barley aleurone cells were isolated employing the aqueous polymer (Dextran and polyethylene glycol) two-phase partition method.

Biosynthesis and localization of phosphatidyl-scyllo-inositol in barley aleurone cells.

A novel isomer of phosphatidylinositol (PI), phosphatidyl-scyllo-inositol, was characterized in the aleurone cells of barley seeds. In this investigation, the subcellular localization of scyllo-PI and the relative rates of biosynthesis and accumulation of [32P]phosphoric acid ([32Pi])-labeled scyllo- and myo-phosphoinositides in the plasma membrane and intracellular membrane pools were investigated. About 25% of the [32Pi]-labeled phospholipids were present in plasma membrane and 75% in intracellular membranes.

Novel Phosphoinositides in Barley Aleurone Cells (Additional Evidence for the Presence of Phosphatidyl-scyllo-Inositol).

A novel isomer of phosphatidylinositol that differs in the structure of the head group was detected in barley (Hordeum vulgare cv Himalaya) seeds. In this paper we describe our efforts to elucidate the structure of the novel isomer. Evidence from a variety of techniques, including chemical modification of in vivo 32Pi- and myo-[3H]inositol-labeled compounds, gas chromatography-mass spectrometry analysis, in vivo incorporation of scyllo-[3H]inositol, and enzymatic studies that suggest that the structure is phosphatidylscyllo-inositol (scyllo-PI), is presented.

Characterization of scyllo-inositol-containing phosphatidylinositol in plant cells.

The structure of in vivo [3H]myo-inositol-labeled phosphatidylinositols in barley seeds were investigated by chemical degradation. In this report we present data that suggests the presence of scyllo-inositol-containing phosphatidylinositol in addition to the commonly occurring myo-inositol-containing phosphatidylinositol.

Evidence of two isomers of phosphatidylinositol in plant tissue.

The structure of phosphatidylinositol in barley (Hordeum vulgare) aleurone layers was investigated by chemical degradation. In vivo myo-[2-(3)H]inositol-labeled phosphatidylinositol was first converted to glycerophosphoinositol and, subsequently, after removal of the glycerol moiety, to inositol monophosphate. Here, we present data that show that, in addition to the commonly occurring 1,2-diacylglycero-3-(d-myo-inositol-1-phosphate), barley aleurone cells contain a novel second isomer of phosphatidylinositol that differs in structure of the head group.