Characterization of the recombinant proteins binding to ELISA plates and to heparin. (A) Amount of protein bound to individual wells as indicated by the sum total of relative binding to a PF4 polyclonal antibody (with PF4 given a value of 1) plus relative binding to a NAP-2 polyclonal antibody (with NAP-2 given a value of 1). (B) Amount of ³H-heparin bound to equal amounts of various recombinant proteins in an ELISA well. Protein 1 = WT PF4; 2 = NPPP; 3 = NNP*P; 4 = NNNP; 5 = PF4, K62; 6 = PF4, K66; 7 = WT NAP-2; and 8 = no recombinant protein.