Facilitation of multimerization.

The propeptide functions in cis and trans to facilitate multimerization. The question of homodimer versus heterodimer formation in VWF biosynthesis was addressed by the coexpression of HPP-VWF (wild-type VWF containing a disrupted furin-cleavage site) with wild-type VWF. When these 2 VWF proteins were coexpressed in HEK293T cells, the resulting protein expression showed nearly exclusive formation of homodimers (lane 1). As a size reference, each single plasmid transfection was included in the gel analysis (WT-VWF, lane 2, and HPP-VWF, lane 3). The immunoblot shown was scanned and the band densities were calculated. Each peak is listed with the scanned area and percentage of total area per gel lane. Only 8.6% of the total VWF detected in lane 1 is heterodimeric. Dimer formation appears to be primarily homodimeric.