A fully functional rod visual pigment in a blind mammal. A case for adaptive functional reorganization?

• Published in: The Journal of biological chemistry 2000-12, Vol.275 (49), p.38674-38679
• Main Authors: Janssen, J W, Bovee-Geurts, P H, Peeters, Z P, Bowmaker, J K, Cooper, H M, David-Gray, Z K, Nevo, E, DeGrip, W J
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Blindness; Cattle; Cloning, Molecular; Conserved Sequence; Light; Mice; Mole Rats - genetics; Molecular Sequence Data; Open Reading Frames; Rats; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Retinal Pigments - chemistry; Retinal Pigments - genetics; Retinal Pigments - physiology; Retinal Rod Photoreceptor Cells - physiology; Retinaldehyde - metabolism; Sequence Alignment; Sequence Homology, Amino Acid; Spalax ehrenbergi; Transducin - metabolism; Transfection
• ISSN: 0021-9258
• DOI: 10.1074/jbc.M008254200

In the blind subterranean mole rat Spalax ehrenbergi superspecies complete ablation of the visual image-forming capability has been accompanied by an expansion of the bilateral projection from the retina to the suprachiasmatic nucleus. We have cloned the open reading frame of a visual pigment from Spalax that shows >90% homology with mammalian rod pigments. Baculovirus expression yields a membrane protein with all functional characteristics of a rod visual pigment (lambda(max) = 497 +/- 2 nm; pK(a) of meta I/meta II equilibrium = 6.5; rapid activation of transducin in the light). We not only provide evidence that this Spalax rod pigment is fully functional in vitro but also show that all requirements for a functional pigment are present in vivo. The physiological consequences of this unexpected finding are discussed. One attractive option is that during adaptation to a subterranean lifestyle, the visual system of this mammal has undergone mosaic reorganization, and the visual pigments have adapted to a function in circadian photoreception.