Improved method for purification of human platelet factor 4 by affinity and ion-exchange chromatography

A simple method for the reproducible purification of human platelet factor 4 (PF4) is described. PF4 is obtained in a highly purified form from platelet concentrate by utilizing a combination of affinity and FPLC ion-exchange chromatography. In every instance, after elution from heparin affinity and cation exchange chromatography, SDS gel electrophoresis reveals a single band attributable to PF4. Moreover, the amino acid composition of PF4 isolated by this method is compatible with that described for a PF4 cDNA clone and with other reported PF4 analysis. The purified protein is used to study in vitro the affinity of PF4 for several glycosaminoglycans (GAGs), by measuring the fluorescence of each PF4-GAG complex bound to fluorescamine. PF4 affinity for GAGs is as follows: heparin greater than heparan sulphate much greater than dermatan sulphate.