EFFECTS OF CHLOROPHYLLIN ON ENCYSTMENT SUPPRESSION AND EXCYSTMENT INDUCTION IN COLPODA CUCULLUS NAG-1: AN IMPLICATION OF CHLOROPHYLLIN RECEPTORMASAYA MORISHITA, FUTOSHI SUIZU, MIKIHIKO ARIKAWA ANDTATSUOMI MATSUOKA
Among the molecules suppressing encystment and inducing excystment of Colpoda cucullus Nag- 1, sodium copper chlorophyllin is the only molecule whose molecular structure is known. The present study showed that sodium iron chlorophyllin also had marked effects. When the encysting cells (2-day-aged immature cysts) of C. cucullus Nag-1 were treated with trypsin (1 mg/mL), excystment was suppressed. In this case, most of the cysts that failed to excyst were alive, because the selective permeability of the plasma membrane of these cysts functioned normally. These results suggest that presumed chlorophyllin receptors which are involved in the induction of excystment may occur on the plasma membranes of the resting cysts. Two-day-aged cysts (immature cysts) are surrounded by thick cyst walls. We assessed whether chlorophyllin and trypsin (23 kDa) penetrate across the cyst wall. When the cysts were immersed in the fluorescent molecule phycocyanin (40 kDa), a vivid phycocyanin fluorescence was observed inside or on the cyst wall, indicating that phycocyanin penetrates across the cyst wall. Judging from these results, chlorophyllin molecules and trypsin flowed in across the cyst wall to act on the receptors located on the plasma membrane.