A Highly Active Anticomplement Factor from the Venom of Naja kaouthia.

A highly active anticomplement factor (cobra venom factor) from the venom of Naja kaouthia in South Yunnan, China was isolated by sequential column chromatography (SP-Sephadex-C-25, Q Sepharose HP and Sephadex G-150). It displays strong anticomplement activities in vitro and in vivo, and has anticomplement activity of 1 515 u per mg. The purified anticomplement factor was homogeneous on SDS-PAGE with a molecular weight of 149 kD. It is composed of three polypeptide chains which are connected by disulfide bonds. The molecular weights of the three chains were determined to be 65.4 kD (alpha-chain), 52.1 kD (beta-chain), and 35.5 kD (gamma-chain). The gamma-chain displayed size heterogeneity, and two bands could be clearly detected in gels. All polypeptide chains were stained with periodate-Schiff reagent, suggesting the presence of carbohydrate. Neutral sugar and sialicacid were determined to be 1.78% and 0.38%, respectively. The isoelectric point of this anticomplement factor was 6.2. Its amino acid composition was analyzed and N-terminal amino acid sequence of each polypeptide chain was determined.