SCALE-ASSOCIATED GLYCOPROTEINS OF SCHERFFELIA-DUBIA (CHLOROPHYTA) FORM HIGH-MOLECULAR-WEIGHT COMPLEXES BETWEEN THE SCALE LAYERS AND THE FLAGELLAR MEMBRANE

Flagellar scales were isolated from the flagellate green alga Scherffe lia dubin. The flagellar scales consist mainly of acidic polysaccharid es (70%) and glycoproteins (10%), and monosaccharide analyses show tha t the scales contain high amounts of unusual 2-keto-sugar acids. Appro ximately, 72 mol% of total carbohydrate is 3-deoxy-manno-2-octulosonic acid, 3-deoxy-5-O-methylmanno-2-octulosonic acid and 3-deoxy-lyxo-2-h eptulosaric acid. Sodium dodecyl sulfate-polyacrylamide gel electropho resis showed the presence of at least 18 different scale-associated pr oteins (SAPs), ranging in apparent molecular mass from 77 kDa to over 300 kDa. Lectin blot analyses performed in combination with glycosidas e treatment, showed that SAPs contained N-glycans of the high-mannose type and the hybrid type, as well as a complex type that was not immun ologically related to higher-plant complex glycans. Most of the SAPs w ere present in two or possibly three high-molecular-weight complexes. In these complexes, individual polypeptides are cross-linked by disulf ide bridges. A polyclonal antibody was raised against a SAP of 126 kDa (SAP126), a glycoprotein present in a high-molecular-weight complex. The SAP126 antibody was used to localize the protein between scale lay er and flagellar membrane. We suggest that these high-molecular-weight complexes link scales to the flagellar membrane.