CHIMERIC PHOTORECEPTOR SYSTEM FROM VERTEB RATE RETINA - IN-VITRO SUBSTITUTION OF RHODOPSIN BY PHOTOSENSITIVE PIGMENT FROM UNICELLULAR ALGA CHLAMYDOMONAS-REINHARDTII
Sn. Korolkov et Rn. Etingof, CHIMERIC PHOTORECEPTOR SYSTEM FROM VERTEB RATE RETINA - IN-VITRO SUBSTITUTION OF RHODOPSIN BY PHOTOSENSITIVE PIGMENT FROM UNICELLULAR ALGA CHLAMYDOMONAS-REINHARDTII, Biologiceskie membrany, 11(2), 1994, pp. 161-168
It has been confirmed that in the vertebrate photoreceptor system stim
ulating 3', 5'-cGMP phosphodiesterase in vitro rhodopsin can be succes
sfully replaced by photosensitive pigment contained in the eyespots of
the unicellular green alga Chlamydomonas reinhardtii. The same effect
has been found with the eyespots from mutant alga cells (without caro
tinoids containing opsin-like protein) but only after their preincubat
ion with 11-cis- or all- trans-retinals. But in the latter case the ex
tent of photostimulated enzyme activation did not depend on the presen
ce of Gpp(NH)p in the incubation medium, being the same with and witho
ut nucleotide. The eyespots of the mutant cells preincubated with both
retinal isomers (unlike to the eyespots which were not preincubated)
induced photostimulation of transducin GTP-ase but the extent of enzym
e activation was considerably lower than that in the presence of rhodo
psin. Five proteins which bind all-trans retinal have been found in th
e eyespot fraction, with two of them (M(r) 21000 and 30000) predominan
tly binding atl-trans-retinal. The 30 kDa protein can also bind 11-cis
-retinal.