Title : Two additional human serum
proteins structurally related to complement
factor H . Evidence for a family of
factor H-related genes
Abstract :
- We identify and characterize two human serum proteins with an apparent molecular mass of 24 and 29 kDa, which are antigenically related to complement factor H
- These proteins represent differently glycosylated forms and are encoded by the same mRNA
- The corresponding cDNA clone is 1051 bp in size and hybridized to a 1.4-kb mRNA derived from human liver
- The predicted translation product represents a protein of 270 amino acids, which displays a hydrophobic leader sequence , indicative of a secreted protein
- The secreted part is organized in four short consensus repeats (SCR) and has a single putative N-linked glycosylation site
- This predicted sequence is closely related to that of the previously described factor H-related proteins h37 and h42, which are also derived from a 1.4-kb mRNA
- Amino acid comparison of these factor H-related proteins showed identical leader sequences , an exchange of three amino acids in SCR1, identical sequences of SCR2 , and a lower degree of homology between SCR3-4 ( h24 and h29 ) and SCR4-5 (h37 and h42)
- In addition, SCR3-4 of h24 and h29 display homology to SCR19-20 of human complement factor H
- The relatedness of structural elements of the factor H-related proteins h24 , h29 , h37 , and h42 and of factor H, suggests a function common to these proteins and indicates the existence of a gene family consisting of factor H and at least two factor H-related genes