Related Experiment Video
Updated: May 5, 2026
Reactivation of Demembranated Cell Models in Chlamydomonas reinhardtii
Published on: May 6, 2022
Reconstitution of biological activity in isoagglutinins fromChlamydomonas eugametos
W L Homan1, P G Hodenpijl, A Musgrave
1Plantenfysiologisch Laboratorium, Universiteit van Amsterdam, Kruislaan 318, NL-1098 SM, Amsterdam, The Netherlands.
Abstract:
Gametes ofChlamydomonas eugametos produce membrane vesicles, called isoagglutinins, which are shed into the culture fluid. It is assumed that they originate from the flagellar membrane for, like flagella, they can bind to the flagellar surface of gametes of the opposite mating type (mt). The composition ofmt (-) isoagglutinin was investigated with respect to this agglutinability. When the agglutination factor present on the surface ofmt (-) isoagglutinins (PAS-1.2) was removed, together with other membrane bound glycoproteins, the membrane vesicles were rendered inactive. They could be reactivated however by incubation with the extracted glycoproteins in a time-and concentration-dependent manner. The agglutination factor proved to be necessary yet sufficient in itself for the reactivation process to occur. Experiments with CsCl density gradients showed that the agglutination factor truly bound to the vesicles during reactivation. Inactivated vesicles derived frommt (+) gametes could be reactivated to gainmt (-) properties. Reactivation was inhibited by prior treatment with trypsin. The results indicate that the agglutination factor inmt (-) isoagglutinins is an extrinsic membrane protein bound to an intrinsic proteinaceous receptor.
Insights
Chlamydomonas eugametos gametes shed membrane vesicles called isoagglutinins. These vesicles can be reactivated to exhibit mating type (-) properties by binding to an agglutination factor, a key finding for understanding cell adhesion.
Area of Science:
- Cell biology
- Molecular biology
- Biochemistry
Background:
- Gametes of Chlamydomonas eugametos produce membrane vesicles (isoagglutinins) originating from the flagellar membrane.
- These isoagglutinins bind to the flagellar surface of gametes of the opposite mating type (mt).
Purpose of the Study:
- To investigate the composition of mt (-) isoagglutinin concerning its agglutinability.
- To elucidate the mechanism of isoagglutinin function and reactivation.
Main Methods:
- Removal and re-incubation of membrane-bound glycoproteins from isoagglutinins.
- CsCl density gradient centrifugation to analyze binding.
- Inhibition studies using trypsin treatment.
Main Results:
- Removal of the agglutination factor (PAS-1.2) inactivated mt (-) isoagglutinins.
- Reactivation occurred upon incubation with extracted glycoproteins in a time- and concentration-dependent manner.
- Inactivated mt (+) vesicles gained mt (-) properties after reactivation, indicating the agglutination factor's crucial role.
Conclusions:
- The agglutination factor is necessary and sufficient for isoagglutinin reactivation.
- The agglutination factor is an extrinsic membrane protein bound to an intrinsic proteinaceous receptor.
- This mechanism is vital for understanding Chlamydomonas cell-cell recognition and adhesion.
