CHAOTROPE-SOLUBLE CELL-WALL GLYCOPROTEINS OF VOLVOX AND SOME MEMBERS OF THE ZYGNEMATOPHYCEAE IMMUNOLOGICALLY RELATED TO THE 150 KDA CELL-WALL GLYCOPROTEIN OF CHLAMYDOMONAS-REINHARDTII

As previously described, the cell wall of Chlamydomonas reinhardtii co ntains several chaotrope-soluble glycoproteins with similar sugar comp ositions, but considerably different proportions of hydroxyproline. Al l these hydroxyproline-containing cell wall glycoproteins are recogniz ed by a polyclonal antibody raised against the purified '150 kDa' cell wall glycoprotein of Chlamydomonas reinhardtii. This antibody also cr oss-reacts with some polypeptides present in the LiCl-extracts from in tact cells of Spirotaenia erythrocephala, Spirotaenia obscura, Volvox aureus, and Volvox globator as revealed by Western blot analyses. Ther efore, an Ige fraction of this particular antibody coupled to CNBr-act ivated Sepharose was used to isolate the immunologically related polyp eptides extracted by aqueous LiCl from intact cells or cell wall prepa rations of different green algae belonging to the Volvocales or to the Zygnematophycene. Different and more or less complex polypeptide patt erns were observed by comparative SDS-PAGE analyses of the polypeptide fractions isolated by immunoaffinity chromatography from extracts of Chlamydamonas reinhardtii, Volvox aureus, Micrasterias rotata, Gonatoz ygon brebissonii and Netrium digitus, respectively, whereas the corres ponding fraction prepared from Spirotaenia erythrocephala contained a predominant '160 kDa' component. Amino acid and sugar analyses reveale d that all these polypeptide fractions contained hydroxyproline (1.0-4 .5 mol%) and the same sugars as the Chlamydomonas cell wall glycoprote ins. However, the relative amounts of these sugars (arabinose, galacto se, glucose, mannose and xylose) were found to be rather different. Th e highest proportion of hydroxyproline (4.5 mol%) and the highest rati o of arabinose:galactose (4.75:1) were determined for the glycoprotein fraction isolated from Spirotaenia erythrocephala indicating that at least the predominant '160 kDa' component is an intrinsic cell wall gl ycoprotein containing hydroxyproline and oligo-arabinosyl side chains. All the polypeptide fractions isolated from the other green algae obv iously also contained chaotropesoluble cell wall glycoproteins as reve aled by the presence of arabinose and hydroxyproline. These findings s how that all the investigated green algae contain chaotrope-soluble ce ll wall glycoproteins immunologically related to the '150 kDa' cell wa ll glycoprotein of Chlamydomonas reinhardtii.