Evidence for a Structural Role of Protein in Algal Cell Walls

Load-extension measurements were made on three filamentous algae before and after either digestion with proteolytic enzymes or treatment with dithiothreitol. Large differences in tensile properties of the walls were observed, particularly after pronase digestion, in two algae, Cladophora and Chaetomorpha, which contain hydroxyproline in the wall. Pronase had little or no effect on a third alga, Nitella, lacking hydroxyproline. A smaller difference was found on treatment with dithiothreitol, a specific reducing agent for disulphide bonds. These results suggest that a hydroxyproline containing protein is a structural component of these algal walls, and that hydroxyproline itself is involved in the carbohydratepeptide linkage.