| Abstract: | The effects of two kinds of molecules, Pb2+ and folic acid, on the formation of clathrin-coated pits and vesicles were studied in the unicellular green alga, Dunaliella salina Teod. Measurable amounts of algal clathrin were obtained in the postmicrosomal fraction from cells treated with folic acid. In contrast, algal clathrin heavy chains were below the detection limit in the postmicrosomal fraction from control and lead nitrate-treated cells. Consistent with the biochemical evidence, electron microscopy showed more clathrin-coated pits and vesicles in folic acid-treated cells compared to control cells or cells treated with lead nitrate alone. Observations of folic acid/lead nitrate-treated cells confirmed the endocytosis of Pb2+ through clathrin-coated pits and vesicles. As additional evidence for clathrin in the folic acid-stimulated cells of Dunaliella salina, clathrin was isolated and, for the first time in algae, the calcium-dependent reconstitution of clathrin cages was successfully obtained in vitro. |
