C-reactive protein in eel: purification and agglutinating activity.

C-reactive protein was highly purified from Japanese eel (Anguilla japonica) serum by precipitation with phosphatidyl-choline and Ca2+. On SDS-PAGE, eel C-reactive protein (eCRP) migrated as a single band with a molecular weight of 24,000 under reducing and 23,500 under non-reducing conditions. The molecular weight of native eCRP was estimated to be 120,000 by Sephacryl S-300 gel filtration. The eCRP was detected within the albumin region on immunoelectrophoresis. The eCRP showed an agglutinating activity against Streptococcus pneumoniae in the presence of Ca2+, and the activity was inhibited by 1 mM EDTA or 1 mM phosphorylcholine (PC). The eCRP also agglutinated rabbit red blood cells (RRBC), but not human and five other kinds of red blood cell. The hemagglutinating activity was inhibited by glucosamine or mannose. The eCRP formed a precipitin line with histone, protamine, poly(L-lysine) and poly(L-arginine) in agarose gel. The serum levels of eCRP were distributed in 6.8 ng/ml-5.3 mg/ml, n = 187, the mean value being 834 ng/ml.