Surface organization and composition of Euglena. II. Flagellar mastigonemes.

The surface of the Euglena flagellum is coated with about 30,000 fine filaments of two distinct types. The longer of these nontubular mastigonemes (about 3 micron) appear to be attached to the paraflagellar rod whereas the shorter nontubular mastigonemes (about 1.5 micron) are the centrifugally arranged portions of a larger complex, which consists of an attached unit parallel to and outside of the flagellar membrane. Units are arranged laternally in near registration and longitudinally overlap by one-half of a unit length. Rows of mastigoneme units are firmly attached to the axoneme microtubules or to the paraflagellar rod as evidenced by their persistence after removal of the flagellar membrane with neutral detergents. SDS-acrylamide gels of whole flagella revealed about 30 polypeptides, of which two gave strong positive staining with the periodic acid-Schiff (PAS) procedure. At least one of these two bands (glycoproteins) has been equated with the surface mastigonemes by parallel analysis of isolated and purified mastigonemes, particularly after phenol extraction. The faster moving glycoprotein has been selectively removed from whole flagella and from the mastigoneme fraction with low concentrations of neutral detergents at neutral or high pH. The larger glycoprotein was found to be polydisperse when electrophoresed through 1% agarose/SDS gels. Thin-layer chromatography of hydrolysates of whole flagella or of isolated mastigonemes has indicated that the major carbohydrate moiety is the pentose sugar, xylose, with possibly a small amount of glucose and an unknown minor component.