HYDROXYPROLINE-CONTAINING AND GLYCINE-RICH CELL-WALL POLYPEPTIDES AREWIDESPREAD IN THE GREEN-ALGAE

The cell walls of the Volvocales studied so far exclusively consist of hydroxyproline-rich glycoproteins, whereas the cell walls of some str ains of Chlorella ellipsoidea have been reported to lack hydroxyprolin e-containing polypeptides. Therefore, we have compared the amino acid compositions of the cells walls of several green algae with special em phasis on the proportions of hydroxyproline. More or less pronounced l evels of hydroxyproline were detected in the cell wall preparations of 15 species belonging to the Volvocales, Chlorococcales, Codiolales, D esmidiales and Zygnematales, respectively. Although the hydroxyproline -contents of the cell wall preparations are affected by growth conditi ons, there is a relationship between the proportions of hydroxyproline present in cell wall polypeptides and the phylogeny of the green alga e. Different species belonging to the same genus contained essentially the same proportions of hydroxyproline in their cell walls. The lowes t levels of hydroxyproline were found in the cell walls of Scenedesmus subspicatus and Pediastrum boryanum which, like Chlorella, belong to the Chlorococcales. On the basis of the amino acid compositions of ins oluble cell wall components, the investigated members of the Chlorococ cales seem to be only distantly related to the Volvocales, but more cl osely related to the Codiolales. The investigated members of the Mesot aeniaceae were found to be heterogeneous with respect to their cell wa ll polypeptides: The Spirotaenia species were found to be more closely related to Mesotaenia and Gonatozygon than to Cylindrocystis and Netr ium. The cell wall preparations of all the investigated green algae co ntained, in addition to hydroxyproline, remarkably high levels of glyc ine and alanine.