FIG. 4.
Requirement of low pH and divalent cations for endosomal cleavage of DHBV L protein. The F3 fraction was used as the source of the endosome. (A) The pH of the digestion buffer was adjusted to 5.5, 6.2, and 7.4. Untreated virions served as a negative control, while DHBV (+) liver lysate served as a positive control. The cleavage products are indicated. (B) The MgCl2 and CaCl2 concentrations were altered as indicated. Note that proteins were separated by 15% PAGE with short electrophoresis. For panel B, visualization of the cleavage products of <20 kDa was improved by increased protein loading.