Gene sharing by delta-crystallin and argininosuccinate lyase.
The lens structural protein delta-crystallin and the metabolic enzyme argininosuccinate lyase (ASL; L-argininosuccinate arginine-lyase, EC 4.3.2.1) have striking sequence similarity. We have demonstrated that duck delta-crystallin has enormously high ASL activity, while chicken delta-crystallin has lower but significant activity. The lenses of these birds had much greater ASL activity than other tissues, suggesting that ASL is being expressed at unusually high levels as a structural component. In Southern blots of human genomic DNA, chicken delta 1-crystallin cDNA hybridized only to the human ASL gene; moreover, the two chicken delta-crystallin genes accounted for all the sequences in the chicken genome able to cross-hybridize with a human ASL cDNA, with preferential hybridization to the delta 2 gene. Correlations of enzymatic activity and recent data on mRNA levels in the chicken lens suggest that ASL activity depends on expression of the delta 2-crystallin gene. The data indicate that the same gene, at least in ducks, encodes two different functions, an enzyme (ASL) and a structural protein (delta-crystallin), although in chickens specialization and separation of functions may have occurred.
Piatigorsky
J
J
Laboratory of Molecular and Developmental Biology, National Eye Institute, Bethesda, MD 20892.
O'Brien
W E
WE
Norman
B L
BL
Kalumuck
K
K
Wistow
G J
GJ
Borras
T
T
Nickerson
J M
JM
Wawrousek
E F
EF
D000595:Amino Acid Sequence; D000818:Animals; D001123:Argininosuccinate Lyase / Q000235:genetics*; D001483:Base Sequence; D002642:Chick Embryo; D003459:Crystallins / Q000235:genetics* / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004372:Ducks; D004625:Embryo, Nonmammalian; D005796:Genes; D006801:Humans; D008190:Lyases / Q000235:genetics*; D008969:Molecular Sequence Data; D009928:Organ Specificity; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D003459:Crystallins; D004247:DNA; D008190:Lyases; D001123:Argininosuccinate Lyase