Two major serum components antigenically related to complement factor H are different glycosylation forms of a single protein with no factor H-like complement regulatory functions.
Factor H is a 150-kDa serum glycoprotein with key regulatory functions in the alternative pathway of complement activation. Two glycoproteins with a molecular mass of approximately 42 and 37 kDa that react with an antiserum against factor H were purified from human plasma. The two glycoproteins have identical N-terminal amino acid sequences but differ in glycosylation. Sequence comparisons indicated that they both correspond to a 1.4-kb mRNA recently cloned from human liver cDNA. The serum concentration of the two glycoproteins together was estimated to be approximately 40 mg/liter. They were found not to exert factor H-like regulatory functions in the alternative pathway. Thus, the 42-kDa glycoprotein described here appears to be distinct from the previously characterized factor H-related protein of similar size, suggesting that human serum contains two factor-H related molecules which both have a molecular mass of 41 to 43 kDa but which differ largely in structure.
Timmann
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C
Bernhard Nocht Institute for Tropical Medicine, Hamburg, F.R.G.
Leippe
M
M
Horstmann
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RD
D000595:Amino Acid Sequence; D003179:Complement C3b / Q000502:physiology; D003180:Complement C3b Inactivator Proteins / Q000276:immunology*; D017242:Complement Factor H; D006023:Glycoproteins / Q000032:analysis* / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012333:RNA, Messenger / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
C493495:CFH protein, human; D003180:Complement C3b Inactivator Proteins; D006023:Glycoproteins; D012333:RNA, Messenger; D003179:Complement C3b; D017242:Complement Factor H