A fully functional rod visual pigment in a blind mammal. A case for adaptive functional reorganization?
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.
Janssen
J W
JW
Department of Biochemistry UMC-160, Institute of Cellular Signalling, University of Nijmegen, Nijmegen, The Netherlands.
Bovee-Geurts
P H
PH
Peeters
Z P
ZP
Bowmaker
J K
JK
Cooper
H M
HM
David-Gray
Z K
ZK
Nevo
E
E
DeGrip
W J
WJ
D000595:Amino Acid Sequence; D000818:Animals; D001766:Blindness; D002417:Cattle; D003001:Cloning, Molecular; D017124:Conserved Sequence; D008027:Light; D051379:Mice; D019577:Mole Rats / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012168:Retinal Pigments / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D012172:Retinaldehyde / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015293:Transducin / Q000378:metabolism; D014162:Transfection
D011994:Recombinant Proteins; D012168:Retinal Pigments; D015293:Transducin; D012172:Retinaldehyde