Abstract
Channerhodopsin-1 (ChR1) and -2 (ChR2) are archaeal type rhodopsins with seven transmembrane domains (ChR1, ABCDEFG and ChR2, abcdefg), and are involved in the phototaxic and photophobic behavior of one of green algae, Chlamydomonas reinhardtii. The ChR1 generates H+-carried photoreceptor current with a maximum absorbance at 510 nm whereas the ChR2 is a light-switched non-selective cation channel with 460 nm maximal action spectrum. To identify the critical domains involved in wavelength sensitivity, homologous recombinations were made between ChR1 and 2 apoproteins at regions connecting the putative transmembrane domains using overlap extension PCR method. The photocurrents of these recombinants were evoked at 477 nm and 532 nm under whole cell patch clamp of transfected HEK293 cells. The photocurrent showed a preference to 477 nm for the recombinants including the fifth transmembrane domain of ChR2. On the other hand the preference was changed to 532 nm when this domain was derived from ChR1. It is suggested that the fifth transmembrane domain of channelrhodopsins may play a critical role in the wavelength preferences. [J Physiol Sci. 2008;58 Suppl:S85]
