Agglutination factor in the cell body of Chlamydomonas eugametos.

Chlamydomonas eugametos gametes agglutinate via the surfaces of their flagella. The mating-type minus (mt (-)) agglutination factor is a high-molecular-weight glycoprotein called PAS-1.2, present on the exterior surface of the flagellar membrane. During flagellar regeneration, mt (-) gametes were able to agglutinate as soon as the flagella protruded as short stumps. This was also observed when protein synthesis was blocked, indicating that gametes possess a pool of PAS-1.2. When the exterior surface of flagella-less gametes was extracted and the proteins were subjected to gel electrophoresis, large quantities of PAS-1.2 were detected. Using anti-PAS-1.2 serum, the presence of PAS-1.2-like material was visualized on the plasma membrane of mt (-) gamete cell bodies. By assaying the biological activity of extracts of the cell bodies and of isolated flagella, it was calculated that the plasma membrane of the cell bodies contains 25 times the activity present in the flagella and could, therefore, represent a large pool of mt (-) agglutination factor.