title: Taxon-specific zeta -crystallin in Japanese tree frog (Hyla japonica) lens.
abstract: The present study demonstrated that the 38-kDa protein, instead of rho-crystallin (36 kDa), is expressed taxon specifically in the lens of Japanese tree frog (Hyla japonica). The 38-kDa protein was distinguished from rho-crystallin expressed in the lenses of bullfrog (Rana catesbeiana) and European common frog (Rana temporaria) immunochemically. Although the N terminus of the 38-kDa protein was blocked, the analyses of partial amino acid sequences showed that the protein was zeta-crystallin. Analysis of cDNA sequence encoding zeta-crystallin of the tree frog lens demonstrated that the deduced protein consisted of 329 amino acids including initial methionine and having 62.2 and 62.9% identity with zeta-crystallin of camel and guinea pig lenses, respectively. The molecular mass of the deduced structure was calculated to be 35,564 Da. zeta-Crystallin of the tree frog lens exhibited the intrinsic enzymatic activity of quinone reductase (EC, NADPH:quinone oxidoreductase). The crystallin specifically catalyzed the reduction of 9,10-phenanthrenequinone (Km, 42 microm) using NADPH (Km, 60 microm) as a cofactor. The enzymatic activity was inhibited by dicumarol, anti-coagulant drug, with IC50 of 4 microm. On gel filtration chromatography, the crystallin was recovered as 150-kDa molecular mass complex, indicating that the crystallin was homotetramer consisting of 38-kDa subunits. The crystallin gene was expressed specifically in the lens. These results show that taxon-specific crystallins such as zeta- and rho-crystallins may be available for the biochemical discrimination of Hyla- and Rana groups among frogs.
authors.affiliation: Department of Chemistry, Faculty of Medicine, Fukui Medical University, 23-3 Shimoaizuki, Matsuoka, Fukui 910-1193, USA. fujiiy@fmsrsa.fukui-med.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Fujii
authors.forename: H
authors.initials: H
authors.lastname: Kimoto
authors.forename: K
authors.initials: K
authors.lastname: Ishikawa
authors.forename: K
authors.initials: K
authors.lastname: Watanabe
authors.forename: Y
authors.initials: Y
authors.lastname: Yokota
authors.forename: N
authors.initials: N
authors.lastname: Nakai
authors.forename: A
authors.initials: A
authors.lastname: Taketo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D015153:Blotting, Western; D002025:Bufonidae; D002162:Camelus; D002850:Chromatography, Gel; D003459:Crystallins / Q000096:biosynthesis* / Q000737:chemistry*; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006168:Guinea Pigs; D007150:Immunohistochemistry; D007700:Kinetics; D007908:Lens, Crystalline / Q000378:metabolism*; D008715:Methionine / Q000737:chemistry; D008969:Molecular Sequence Data; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D013045:Species Specificity; D013379:Substrate Specificity; D014018:Tissue Distribution
chemical_list: D003459:Crystallins; D018076:DNA, Complementary; D012333:RNA, Messenger; D009249:NADP; D008715:Methionine; D016660:NAD(P)H Dehydrogenase (Quinone)