COMPLEMENT COMPONENT GENES OF JAPANESE FLOUNDER Paralichthys olivaceus

Laboratory of Genetics and Biochemistry, Tokyo University of Fisheries, Konan 4-5-7, Minato-ku, Tokyo 108-8477, Japan

We isolated two types of complement regulatory protein like-cDNAs (HCRF-1 and HCRF-2) and four complement component cDNAs (C3, C7, C8 beta and C9) from the Japanese flounder (Paralichthys olivaceus). HCRF-1 and HCRF-2 are composed of 7 and 12 tandem short consensus repeats (SCRs). The SCRs were closely related to those of the previously described complement regulatory plasma protein of barred sand bass (SBP1). The deduced amino acid sequences of C7, C8 beta and C9 of Japanese flounder all exhibit the following domains: thrombospondin, LDL receptor, EGF precursor and a second thrombospondin. Only one of the flounder C7 factor I domain was complete, with several amino acids deleted from the C-terminus of the second. Two thrombospondin domains are present in Japanese flounder C9, a feature which has more resemblance to human C8 alpha and C8 beta than with human C9. Cysteine residues were highly conserved all components regardless of flounder or human origin. Collectively these features emphasize the great similarity among the terminal complement family. Complement system is presumed to have ancient genetic orientation. Six human complement regulatory protein gene types are located within the regulators of the complement activation (RCA) on the arm of chromosome 1, band q3.2. The C6 and C7 genes are arranged in a 3^'-to-3^' orientation and are 160 kbp apart. On the other hand, the C8 alpha and C8 beta genes are arranged in a 5^'-C8 alpha to-3^'-C8 beta. To analyze these genes in Japanese flounder, we constructed the genomic BAC library and isolated BAC clones of C7 and C8 beta. Now we are also trying to isolate BAC clones of HCRF-1 and HCRF-2.