title: Identification and characterization of nonsedimentable lipid-protein microvesicles.
abstract: Previously uncharacterized lipid-protein microvesicles have been isolated from young and senescing bean cotyledon tissue. The microvesicles are nonsedimentable and enriched in phospholipid degradation products (free fatty acids, long-chain aldehydes, and long-chain hydrocarbons). They range from 70 to 170 nm (radius) with a mean radius of 132 nm, and it is clear from freeze-fracture electron micrographs that they are bilayered in nature. Nonsedimentable lipid-protein microvesicles containing the same products of phospholipid degradation but smaller were also formed in vitro when smooth microsomal membranes from young cotyledon tissue were treated with Ca2+ to stimulate enzymatic degradation of phospholipids. The data suggest that these microvesicles comprise an intermediate stage of membrane lipid deterioration. They appear to serve as a vehicle for moving phospholipid degradation products out of membranes into the cytosol during senescence and perhaps also during normal membrane lipid turnover.
authors.affiliation: Department of Horticultural Science, University of Guelph, Guelph, ON, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Yao
authors.forename: G
authors.initials: G
authors.lastname: Paliyath
authors.forename: R W
authors.initials: RW
authors.lastname: Humphrey
authors.forename: F R
authors.initials: FR
authors.lastname: Hallett
authors.forename: J E
authors.initials: JE
authors.lastname: Thompson