The second component (C2n) of the nurse shark complement system: purification, physico-chemical characterization and...

C2n was isolated and purified from nurse shark serum by initial cold low ionic strength precipitation, followed by chromatography on DE-52 cellulose, hydroxylapatite and filtration on BioGel A-0.5. The molecular weight, determined by gel filtration and PAGE, was 170K daltons and 180K daltons respectively. The molecule retained 100% activity after heating for 2 hours at 56 degrees C. Optimal temperature and time for C2n fixation was 30 degrees C and 20 minutes respectively. Experiments were carried out to determine whether C2n and C4gp could replace each other in the lysis of cellular intermediate EAnC1n (with which both components are compatible) when the remaining homologous and heterologous complement components were supplied. Results showed that lysis only occurred with the homologous components indicating an incompatibility between C2n and C2gp and C4gp and C3n. Results from interference studies indicated that C4gp and C2n interfere with each others binding and/or interaction with EAnC1n.