LOCALIZATION OF BLEPHARISMIN PHOTOSENSORS AND IDENTIFICATION OF A PHOTORECEPTOR COMPLEX MEDIATING THE STEP-UP PHOTOPHOBIC RESPONSE OF THE UNICELLULAR ORGANISM, BLEPHARISMA

Photosensitivity for the step-up photophobic response of Blepharisma i s localized in the anterior 1/5 of the cell body, Blepharismin pigment , which is believed to be a photoreceptor pigment mediating the step-u p photophobic response of the cells, was separated into five types of blepharismin (BL-1, -2, -3, -4 and -5), Blepharismin-1, -3, -4 and -5 were localized in the posterior 4/5, while BL-2 was located over the e ntire cell body; the anterior end, which is the photosensitive region, contained only BL-2. The results indicate that a functional photorece ptor pigment mediating the step-up photophobic response is BL-2, Hydro xylapatite chromatography revealed that BL-2 was bound to a 200 kDa me mbrane protein, We concluded that a photoreceptor mediating the step-u p photophobic response was a BL-2/200 kDa protein complex.