ABSTRACT
The relative amounts of Concanavalin A (Con A) bound by gamete and vegetative flagella of both mating types (mt (+) and mt (-)) of Chlamydomonas eugametos were determined using (125)I-Con A. Con A agglutinated all cell types by cross-linking their flagella in a random manner. No correlation was found between the extent of Con A-binding and Con A-mediated isoagglutination. Con A inhibited the sexual interaction between gametes at various levels. In mt (+) gametes it blocked sexual agglutination, whereas in mt (-) gametes it prevented papillar fusion. By SDS-gel electrophoresis nine Con A-binding components were found to be present in flagella. However, it was not possible to allocate a role in sexual agglutination to any of these components since they were present in all cell types, including vegetative cells which are not able to sexually agglutinate.
ABSTRACT
The flagellar glycoproteins exposed on Chlamydomonas eugametos gametes were labeled by means of lactoperoxidase, diiodosulfanilic acid and chloramine T, and characterised in SDS-electrophoresis gels. The medium from gamete cultures contains particles (isoagglutinins) that agglutinate gametes of the opposite mating type. When crude preparations of these particles were subjected to isopycnic centrifugation in a caesium chloride gradient, two bands of particles were found. The lighter, active band consisted of membrane vesicles. The denser, inactive band consisted of cell wall material. The active band had the same glycoprotein composition as membrane vesicles artificially made from isolated flagella. Preparations of glagella were also separated on a caesium chloride cushion into pure flagella and cell wall material. The flagella, but not the cell wall material, isoagglutinated opposite gametes. Again the glycoprotein composition of pure flagella was similar to that of pure isoagglutinin vesicles. No difference was detected between the protein and glycoprotein compositions of flagella and isoagglutinins from both mating types.