Purification and characterization of anticomplement factor (cobra venom factor) from the Naja naja atra venom

Anticomplement factor (cobra venom factor) from the venom of Naja naja atra was purified by means of successive chromatography on DEAE-cellulose, Sephadex G-200 and Sepharose CL-6B. The purified anticomplement factor was homogeneous as judged by polyacrylamide discontinuous gel electrophoresis at pH 9.4. The yield from 3.0 g of the crude venom was approx. 28 mg. The molecular weight was estimated to be about 156 000 by SDS-polyacrylamide gel electrophoresis. The isoelectric point was about 5.2. SDS-polyacrylamide gel electrophoresis of the anticomplement factor in the presence of dithiothreitol demonstrated that the molecule possesses three different polypeptide chains cross-linked covalently to one another by disulfide bridge(s). By SDS-polyacrylamide gel electrophoresis, the molecular weight of each subunit was determined to be approx. 77000, 47500 and 29 000, respectively. All subunits were stained with Coomassie brilliant blue G-250 and periodate-Schiff reagent, indicating these subunits to be glycoprotein. Distribution of the anticomplement factor in various snake venoms, which shows cross-reactivity against the anti-Naja naja atra anticomplement factor antiserum, was examined. From the results, all venoms belonging to cobra family in the Elapidae tested so far were found to contain such cross-reactivity.