SP-40,40, a newly identified normal human serum protein found in the SC5b-9 complex of complement and in the immune deposits in glomerulonephritis.
We report herein the isolation and initial characterization of a novel protein, termed SP-40,40, which is present at moderate levels (35-105 micrograms/ml) in normal human serum. SP-40,40 is deposited in the renal glomeruli of patients with glomerulonephritis but is not found in normal glomeruli. The protein is a heterodimeric structure of relative molecular mass 80 kD, both chains of which are of a similar size (40 kD). The amino-terminal sequences of both chains are unrelated to one another and possess no significant homology to any known protein sequence. The tissue distribution of SP-40,40 closely resembles that of the terminal complement components and its physicochemical properties are similar to, but distinct from, those of the S protein of complement. We have identified SP-40,40 in the SC5b-9 complex of complement and have demonstrated incorporation of labeled SP-40,40 into this complex. These data suggest that SP-40,40 is an additional component of SC5b-9.
Murphy
B F
BF
Department of Nephrology, Royal Melbourne Hospital, Australia.
Kirszbaum
L
L
Walker
I D
ID
d'Apice
A J
AJ
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology; D001345:Autoradiography; D001798:Blood Proteins / Q000032:analysis* / Q000302:isolation & purification*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D051152:Clusterin; D003182:Complement C5 / Q000032:analysis*; D050776:Complement C5b; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005921:Glomerulonephritis / Q000276:immunology*; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D007118:Immunoassay; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D007678:Kidney Glomerulus / Q000032:analysis*; D008297:Male; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D008970:Molecular Weight; D019096:Vitronectin
D000911:Antibodies, Monoclonal; D001798:Blood Proteins; C495242:CLU protein, human; D051152:Clusterin; D003182:Complement C5; D006023:Glycoproteins; D018832:Molecular Chaperones; D019096:Vitronectin; D050776:Complement C5b