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First published online March 9, 2004
Journal of Experimental Biology 207, 1387-1398 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00897
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The occurrence of two types of hemopexin-like protein in medaka and differences in their affinity to heme

Makoto Hirayama, Atsushi Kobiyama*, Shigeharu Kinoshita{dagger} and Shugo Watabe{ddagger}

Laboratory of Aquatic Molecular Biology and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan

{ddagger} Author for correspondence (e-mail: awatabe{at}mail.ecc.u-tokyo.ac.jp)

Accepted 26 January 2004

Full-length cDNA clones encoding two types of hemopexin-like protein, mWap65-1 and mWap65-2, were isolated from the HNI inbred line of medaka Oryzias latipes. The deduced amino acid sequence of mWap65-2 resembled mammalian hemopexins more closely than that of mWap65-1. Histidine residues required for the high affinity of hemopexins for hemes were conserved in mWap65-2, but not in mWap65-1. Surprisingly, mWap65-1, but not mWap65-2, showed heme-binding ability as revealed by hemin–agarose affinity chromatography, even though mWap65-1 lacked the essential histidine residues. Furthermore, RT-PCR analysis of different tissues demonstrated that the transcripts of mWap65-2 were restricted to liver, whereas those of mWap65-1 were found in various tissues including liver, eye, heart and brain. Quantitative RT-PCR revealed that transcripts of mWap65-2 were expressed earlier than those of mWap65-1 during ontogeny. However, the accumulated mRNA levels of both mWap65-1 and mWap65-2 did not differ significantly in fish acclimated to either 10°C or 30°C for 5 weeks. These characteristics suggest that the two proteins have different physiological functions and that mWap65-2 is not a hemopexin.

Key words: eurythermal fish, medaka, Oryzias latipes, temperature acclimation, mWap65-1, mWap65-2, heme-binding ability, hemopexin




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M. Nakaniwa, M. Hirayama, A. Shimizu, T. Sasaki, S. Asakawa, N. Shimizu, and S. Watabe
Genomic sequences encoding two types of medaka hemopexin-like protein Wap65, and their gene expression profiles in embryos
J. Exp. Biol., May 15, 2005; 208(10): 1915 - 1925.
[Abstract] [Full Text] [PDF]


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