Extracellular agglutination factor of myxamoebae produced by Dictyostelium discoideum NC-4

A non-dyalyzable specific agglutination factor of myxamoebae obtained from culture broth during the growth phase of Dictyostelium discoideum NC-4 was thermostable but the agglutination activity disappeared below pH 5.0. In the case of formalinized myxamoebae, digestion of the factor with Pronase decreased the activity, but periodate treatment of the factor did not affect the activity. Myxamoebal agglutination by this factor was inhibited by the addition of uronic acid, polyuronide (protuberic acid), and cell-surface polysaccharide prepared from the myxamoebae, but the agglutination was not affected by citric acid or glycine. The factor was purified by ethanol precipitation, column chromatography using DEAE-cellulose and Sepharose-2B, and zone electrophoresis. Chemical analysis of the purified factor gave 61.0% carbohydrate and 26.1% protein, and glucose, mannose, xylose and rhamnose (molar ratios of 9,3 : 3.2 : 2.1 : 1.0) were detected as the component sugars. The content of uronic acid was 12.9%. When the myxamoebae of the growth phase were starved in Millipore-supporting medium, the agglutination activity was detected in the supernatant of the medium.