The Photosensation Mechanism Study Of C.elegans Taste Receptor Homolog LITE-1

For many organisms,turning the light in the environment into a biological signal is the key to survival,such as DNA repair and its metabolic changes in light stimulating bacteria,light-evading reactions of single-celled organisms,Photosynthesis in plants and light perception in animal vision and non-vision.Although there are a variety of reactions to light,there are only six kinds of light-sensitive protein families in the world.They are Rhodopsins,Phytochromes,Xanthopsins,Cryptochromes,Phototropins and BLUF proteins,they can be used to transduce light signals.C.elegnas have become an increasingly popular model organism for sensory conduction studies and have found that they can respond quickly and strongly to blue light or shorter wavelengths of UV light,but little is known about the mechanism of this light perception.Previous studies have shown that this reaction is mediated by the membrane protein LITE-1.LITE-1 protein is expressed in multiple sensory neurons,such as ASJ,ASB,ASK,ASH,ASI,AWC and ADL,and these sensory neurons play a rapid and strong avoidance response to short wavelength light.Our study showed that LITE-1 protein had no homology with the above six photoproteins,and the topological structure of LITE-1 protein was opposite to the traditional seven transmembrane proteins.We used a fermentor culture method to collect a large number of muscle cells in the expression of LITE-1 protein nematodes.And the LITE-1 protein was purified by affinity chromatography.From the analysis of nematode behavior and muscle cell calcium imaging and the absorption spectrum of LITE-1 protein,LITE-1 can absorb UVA and UVB,and the ability to absorb UV light is dependent on its own conformation.The two tryptophan residues W77 and W328 of LITE-1 protein play an important role in UVA and UVB uptake mechanisms,in which UVA is absorbed and the other two amino acid residues S226 and A332 participate.Therefore,the LITE-1 protein,which is homologous to the nematode taste receptor,is a novel photoreceptor protein.To better demonstrate the role of tryptophan residues in the uptake of UVB,the tryptophan residue was introduced into the GUR-3,a homologue of the LITE-1 protein,by genetic engineering.The results showed that the introduced tryptophan residue can turn the original GUR-3,which cannot uptake UVB light,into absorbing UVB.