BIOCHEMICAL-CHARACTERIZATION OF PLASMA-MEMBRANE VESICLES OF CYANOPHORA-PARADOXA

Plasma membrane vesicles (PMVs) were isolated PA: from Cyanophora para doxa Korshikov (Glaucocystophyta) and purified by differential and suc rose density gradient centrifugation PMVs were identified ultrastructu rally and biochemically using marker enzymes. Analysis of monosacchari des revealed a sugar content of 37.3% of dry weight of delipidated PMV s with high amounts of fucose (28 mol% of total carbohydrate), galacto se (23%), mannose (21%) and the minor constituents xylose, rhamnose, g lucose and N-acetylglucosamine Proteins were analyzed by SDS-PAGE. Mor e than 20 polypeptides were resolved and several were identified as gl ycopeptides, as shown by PAS staining and lectin blots. Fucose linked alpha-1-->6 to N-acetylglucosamine (AAA-binding), mannose linked alpha -1-->2,3,6 to mannose (GNA-binding) and terminally bound galactose (RC A-binding) were identified on several polypeptides. Sterols (p-sitoste rol and an additional unknown sterol, 40% of total lipids) and diacylg lycerol (43%) are the major lipid components in the PMVs of C. paradox a. Minor components are PE, PC, PG and an unknown glycolipid. Fatty ac id analysis revealed 12 different fatty acids, predominantly 16:0, 18: 0 and the polyunsaturated acids 20:4 and 20:5 (together 69% of total f atty acids). alpha-Linolenic acid, common in higher plant PMs, could o nly be detected as a minor constituent (< 1 %) of PMVs of C. paradoxa.