Abstract
Abstract: :
Purpose: Mammalian species express high levels of the water-soluble ALDH3A1 in corneal epithelium with the exception of rabbit, which expresses ALDH1A1 rather than ALDH3A1. Several hypotheses, which include catalytic and/or structural functions, have been made about the role of the ALDHs expressed in cornea. The aim of the present study was to clone the rabbit ALDH1A1 cDNA, and express and characterize the ALDH1A1 protein. Methods: Using the mouse ALDH1A1 cDNA we screened a rabbit corneal cDNA library and cloned the ALDH1A1 cDNA. The rabbit and human ALDH1A1 cDNAs were subcloned into baculovirus, and recombinant viruses were used to produce these proteins in Spodoptera frugiptera (Sf9) cells. Results: The rabbit ALDH1A1 cDNA is 2,073 bp in length excluding the poly(A+) tail, and has 5' and 3' nontranslated regions of 46 bp and 536 bp respectively. This ALDH1A1 cDNA encodes a protein of 496 amino acids (Mr = 54,340), which is: 85-89% identical to mouse, rat, horse, sheep, and human ALDH1A1 proteins, and approximately 70% identical to human and mouse ALDH1A2 or ALDH1A3 proteins. Our preliminary studies on the metabolic activities of the Sf9 cells containing either the rabbit or the human ALDH1A1 showed that the rabbit ALDH1A1 is catalytically inactive, whereas the human ALDH1A1 is fully active for a wide variety of aldehydes. Conclusions: The rabbit corneal ALDH1A1 may represent a crystallin involved in the maintenance of corneal transparency. Additional biochemical and biophysical studies with our purified rabbit ALDH1A1 protein should provide valuable information about the role of water-soluble proteins expressed in the corneal epithelium.
Keywords: 370 cornea: basic science • 526 protein purification and characterization • 527 protein structure/function