Molecular Analysis of Complement Regulatory Protein-Like cDNA Composed of 12 Tandem SCRs from the Japanese Flounder.

Abstract

We cloned and analyzed a complement regulatory protein-like cDNA termed HCRF-2 from a liver cDNA library of the Japanese flounder Paralichthys olivaceus.The cDNA was 3101 bp in length and the predicted trans lation product of 737 amino acids contains a hydrophobic signal sequence followed by a stretch of 12 short consensus repeats (SCRs).These SCRs were closely related to those of the previously described SBP1 of complement regulatory plasma protein of barred sand bass. SCR domains Nos. 1 to 12 of HCRF-2 resembled domains Nos. 1 to 10 of SBP1. Recently, we reported a complement regulatory protein-like cDNA designated HCRF that contained 7 SCRs. SCR domains Nos. 2 to 7 of HCRF resembled domains Nos. 12 to 17 of SBP1, but SCR domains of HCRF did not resemble those of HCRF-2.In these comparisons, schematic models of HCRF, HCRF-2 and SBP1 clearly showed their close relationship, indicating that these cDNAs originated from the same ancestral gene.

The complement system in teleosts

“…Another protein with high similarity to SBP1, SBCFR-1, has been cloned from the same species and is comprised of 3 SCR [58]. Two cDNA clones of similar molecules have been identified from the Japanese flounder [59,60]. Factor H-like clones have been isolated from trout and sequence analysis has shown high homology with the SBP1 protein from the barred sand bass [61].…”

A CD46-like Molecule Functional in Teleost Fish Represents an Ancestral Form of Membrane-Bound Regulators of Complement Activation

“…Loci of each group form a compact cluster, and, in the human genome, the group 1 cluster and the group 2 loci are also located in proximity, forming a RCA gene cluster (20)(21)(22). Genomic arrangement of the RCA genes and their clustering are diverse among species analyzed to date, such as mice (23,24), chicken (25,26), frog (27), and teleost, which is the most common group of the ray-finned bony fish (28)(29)(30)(31)(32)(33)(34).…”