DNA Aggregating Protein from Carp (Cyprinus capio) Eggs

Hemagglutinating activity for glutaraldehyde-fixed, trypsinized human and rabbit erythrocytes was obtained from carp (Ciprinus capio) egg extract. This activity was inhibited by sulfated glycans such as heparin and fucoidan, and salmon testis DNA (stDNA), but not by mono- and oligosaccharides. The active fraction from hydroxyapatite column, HA400, caused aggregation of stDNA at a concentration of 125 μg/ml. HA400-induced aggregation was inhibited by heparin and fucoidan at the concentrations of 25 and 50 μg/ml, respectively. HA400 also bound to short size single- or double-stranded oligonucleotide in dot blot hybridization analysis using 32P-labeled probe. HA400 was further purified by heparin-Sepharose column chromatography, and consequently, active fractions (HS2, HS3 and HS4) were obtained. Hemagglutinating activities of HS2 and HS4 were 16 and 32 times higher than that of HS3, respectively. In contrast, HS3 showed the highest DNA aggregating activity among these fractions, indicating that the activities of DNA aggregation and hemagglutination were separated by heparin-Sepharose column chromatography. HS3-induced stDNA aggregation was inhibited by 0.5 M NaCl or above. Southwestern blot analysis revealed that the DNA aggregating protein (DAP) possessing oligonucleotide-binding capacity was the 18 kDa protein. The N-terminal amino acid sequence of DAP was LKEGECEVCVGFLGR having partial homology with DNA-binding protein HU-α, but showed no homology with nucleohistone proteins. These results indicate that there is a novel, non-histone DAP in carp eggs.