Characterization of CR1- and membrane cofactor protein-like proteins of two primates.
We have identified and characterized C3b binding proteins of two primates, orangutan (Pongo pygmaeus) and gorilla (Gorilla gorilla). Detergent solubilized 125I surface-labeled E and PBMC were subjected to affinity chromatography with homologous or human iC3/C3b. These ligands bound a 225,000 single chain protein from orangutan E and PBMC and a 220,000 protein from gorilla E. Proteins of the same Mr were immunoprecipitated by a rabbit polyclonal and two murine mAb to the human CR1 (CD35). The C3b binding protein of gorilla E aligned with that of the common human CR1 polymorphic size variant. Human or orangutan iC3 was also a ligand for a surface-labeled protein doublet of 59,000 and 65,000 from orangutan E. The doublet pattern and mol wts are similar to membrane cofactor protein (or CD46). Further, this doublet was immunoprecipitated by a mAb to human MCP. The MCP-like protein doublet was not isolated from gorilla or human E. Decay accelerating factor (DAF) of orangutan E was also identified and was structurally and antigenically distinct from the MCP-like protein. Orangutan or gorilla E preparations were a cofactor for the cleavage of human iC3 by human factor I and produced the same cleavage fragments as human CR1. Cofactor activity of orangutan E was partially inhibited by preclearance of CR1 and more completely inhibited by preclearance of MCP. Cofactor activity of gorilla E was inhibited by coincubation with a monoclonal antibody to human CR1. These data indicate that the orangutan and gorilla high m.w. proteins are equivalent to human CR1. The orangutan E membrane protein doublet with m.w. of 59,000 and 65,000 possesses biochemical, antigenic, and functional properties of human membrane cofactor protein.
Nickells
M W
MW
Howard Hughes Medical Institute Laboratories, Washington University School of Medicine, St. Louis, MO 63110.
Atkinson
J P
JP
D000818:Animals; D015703:Antigens, CD; D002846:Chromatography, Affinity; D003176:Complement C3 / Q000302:isolation & purification / Q000378:metabolism; D004912:Erythrocytes / Q000032:analysis; D006071:Gorilla gorilla / Q000502:physiology*; D015186:Hominidae / Q000502:physiology*; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000302:isolation & purification*; D008970:Molecular Weight; D011148:Pongo pygmaeus / Q000502:physiology*; D011951:Receptors, Complement / Q000302:isolation & purification* / Q000378:metabolism; D017463:Receptors, Complement 3b
D015703:Antigens, CD; D003176:Complement C3; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D011951:Receptors, Complement; D017463:Receptors, Complement 3b