SP-40,40 is an inhibitor of C5b-6-initiated haemolysis.
This study examines the function of SP-40,40, a newly identified component of the SC5b-9 complement complex, in the regulation of the terminal complement pathway. Purified SP-40,40 was shown to inhibit, in a dose-dependent manner, C5b-6-initiated haemolysis. Apparently additive inhibition was also demonstrated in conjunction with complement S-protein, although SP-40,40 appears to be the more potent inhibitor on an equimolar basis. The data suggest that SP-40,40, like S-protein, probably combines with the nascent C5b-7 complex, forming a cytolytically inactive SC5b-7 - SP-40,40 complex. Preparations of S-protein, purified by an established technique, were shown to be contaminated with SP-40,40. Preparations of affinity-purified SP-40,40 were also shown to contain S-protein, suggesting that these proteins may be partially complexed in plasma.
Murphy
B F
BF
Department of Medicine, University of Melbourne, Australia.
Saunders
J R
JR
O'Bryan
M K
MK
Kirszbaum
L
L
Walker
I D
ID
d'Apice
A J
AJ
D000818:Animals; D001798:Blood Proteins / Q000276:immunology / Q000302:isolation & purification / Q000494:pharmacology*; D051152:Clusterin; D003165:Complement System Proteins / Q000502:physiology*; D004912:Erythrocytes / Q000187:drug effects / Q000276:immunology; D006023:Glycoproteins; D006168:Guinea Pigs; D006461:Hemolysis / Q000187:drug effects* / Q000276:immunology; D006801:Humans; D066298:In Vitro Techniques; D018832:Molecular Chaperones
D001798:Blood Proteins; C495242:CLU protein, human; D051152:Clusterin; D006023:Glycoproteins; D018832:Molecular Chaperones; C050974:complement C5b-6 complex; D003165:Complement System Proteins