Isolation and physicochemical characterization of the half‐unit membranes of oilseed lipid bodies

Abstract

The lipid‐free residue of lipid body membranes was isolated from quiescent peanuts and was physicochemically characterized. The preponderant component of the residue was proteinaceous and consisted of at least two polypeptides according to ultracentrifugation, gel filtration, gel electrophoresis and HPLC. The molecular weight of the principal polypeptide was between 10,000 and 16,000 daltons. Only one antigen, immunochemically unique with respect to other peanut components, was detected. Spectral analyses indicated the presence of a protoheme and revealed conformational modes of β‐sheet and unordered structure but no α‐helix. The amino acid composition was similar to that of an integral membrane polypeptide rather than to those of peripheral membranes or other plant polypeptides. The hydrophobicity, conformation and quantitative content of polypeptides were suitable for the existence of a monolayer at the lipid body‐cytoplasm interface. The results indicated that lipid body coatings physicochemically resemble membranes of intracellular organelles and supported the morphological concept that the coatings are half‐unit biological membranes. Reutilization of lipid body membranes appeared possible after lipid depletion during seed germination.

The Accumulation of Oleosins Determines the Size of Seed Oilbodies inArabidopsis

“…Chemical and ultrastructural analysis reveals that seed oilbodies are surrounded by a phospholipid monolayer where the aliphatic chains are oriented to the triglyceride lumen and the phosphate groups toward the cytoplasm (Yatsu and Jacks, 1972;Jacks et al, 1990). Chemical analysis also reveals that 1 to 4% by weight of seed oilbodies is composed of proteins (Huang, 1992;.…”

The structure and biogenesis of plant oil bodies: the role of the ER membrane and the oleosin class of proteins

“…Moreover, if the oil bodies are washed with solvents such as diethyl ether to extract the TAG without disrupting the pellicle, then the collapsed structures ("ghosts") observed by EM look similar to a unit membrane. This has led to the hypothesis that the oil body may be bounded by a half-unit membrane [21,23].…”

Production of biologically active hirudin in plant seeds using oleosin partitioning

“…Although oilseed rape is generally not wet milled, this process could be adapted from existing equipment and procedures routinely used for wet milling of other crops such as corn. Similarly, it has been shown [17] that equipment presently used in the dairy industry for the separation of milk products is suitable for the separation of oil bodies following aqueous extraction. Production of recombinant proteins in seeds also offers several distinct advantages over synthesis in bacteria and yeast.…”