Figure 3.

Characterization of PCSK9 protein in human serum. When immunoprecipitated from human serum and analyzed in our laboratory by subsequent western blotting under reducing and denaturing conditions, PCSK9 migrates as an intact band (top arrow) that co-migrates with recombinant PCSK9 protein (rPCSK9) [51,60]. In addition, a band of approximately 55 kD is also present (middle arrow), and this band had been described as representing a furin cleavage product of the intact protein [49]. The band at the very bottom of the blot represents the propeptide which remains tightly but non-covalently associated during the immunoprecipitation step, but is subsequently separated by denaturation prior to western blotting (lower arrow).