The occurrence of two types of hemopexin-like protein in medaka and differences in their affinity to heme.
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 degrees C or 30 degrees C for 5 weeks. These characteristics suggest that the two proteins have different physiological functions and that mWap65-2 is not a hemopexin.
Hirayama
Makoto
M
Laboratory of Aquatic Molecular Biology and Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Kobiyama
Atsushi
A
Kinoshita
Shigeharu
S
Watabe
Shugo
S
D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D018076:DNA, Complementary / Q000235:genetics; D004926:Escherichia coli / Q000378:metabolism; D005822:Genetic Vectors; D006418:Heme / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism*; D015151:Immunoblotting; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D009990:Oryzias / Q000097:blood* / Q000235:genetics; D010802:Phylogeny; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013696:Temperature
D018076:DNA, Complementary; D012333:RNA, Messenger; D006418:Heme; D006639:Histidine