cDNA structure of rabbit C4b-binding protein alpha-chain. Preserved sequence motive in complement regulatory protein modules which bind C4b.
A full length cDNA clone for the alpha-chain of the rabbit complement regulatory protein C4b-binding protein (C4BP) was isolated from a liver cDNA library. The clone encoded an open reading frame of 597 amino acids, which included a signal peptide, eight short consensus repeats (SCR) and a carboxy terminal non-repeat region. Gel filtration of rabbit plasma and testing of fractions for factor I cofactor activity (C4BP-like) revealed two peaks of activity, the one with highest molecular weight corresponding in size to that of human C4b-binding protein. Comparison of the rabbit C4BP alpha-chain sequence with other SCR containing C3b/C4b binding proteins revealed highest sequence similarities between the second SCRs in C4BP from rabbit, human and murine species and SCRs at corresponding position in complement receptor 1 (CR1) whereas in decay accelerating factor (DAF), the third SCR was most similar. A conserved sequence motive was identified in these C4b-binding SCRs.
García de Frutos
P
P
Department of Clinical Chemistry, University of Lund, Malmö General Hospital, Sweden.
Dahlbäck
B
B
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D015935:Complement C4b / Q000378:metabolism*; D003169:Complement Inactivator Proteins; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000737:chemistry*; D006023:Glycoproteins; D008969:Molecular Sequence Data; D011817:Rabbits
D002352:Carrier Proteins; D003169:Complement Inactivator Proteins; D018076:DNA, Complementary; D006023:Glycoproteins; D015935:Complement C4b