Analysis of the blind Drosophila mutant ninaB identifies the gene encoding the key enzyme for vitamin A formation invivo.
Visual pigments (rhodopsins) are composed of a chromophore (vitamin A derivative) bound to a protein moiety embedded in the retinal membranes. Animals cannot synthesize the visual chromophore de novo but rely on the uptake of carotenoids, from which vitamin A is formed enzymatically by oxidative cleavage. Despite its importance, the enzyme catalyzing the key step in vitamin A formation resisted molecular analyses until recently, when the successful cloning of a cDNA encoding an enzyme with beta,beta-carotene-15,15'-dioxygenase activity from Drosophila was reported. To prove its identity with the key enzyme for vitamin A formation in vivo, we analyzed the blind Drosophila mutant ninaB. In two independent ninaB alleles, we found mutations in the gene encoding the beta,beta-carotene-15,15'-dioxygenase. These mutations lead to a defect in vitamin A formation and are responsible for blindness of these flies.
von Lintig
J
J
Albert-Ludwig University of Freiburg, Institute for Biology I, Neurobiology and Animal Physiology, Hauptstrasse 1, D-79104 Freiburg, Germany. lintig@uni-freiburg.de
Dreher
A
A
Kiefer
C
C
Wernet
M F
MF
Vogt
K
K
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D001766:Blindness / Q000235:genetics*; D002645:Chickens; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000201:enzymology / Q000235:genetics*; D005260:Female; D006579:Heterozygote; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010105:Oxygenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017354:Point Mutation; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012243:Rhodopsin / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014801:Vitamin A / Q000096:biosynthesis; D014802:Vitamin A Deficiency; D050559:beta-Carotene 15,15'-Monooxygenase
D029721:Drosophila Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; C493360:ninaB protein, Drosophila; D014801:Vitamin A; D012243:Rhodopsin; D010105:Oxygenases; D050559:beta-Carotene 15,15'-Monooxygenase