FIGURE 1.

Sequential UBC7-gp78-mediated and UbcH5a-CHIP-Hsc70-Hsp40-mediated CYP3A4 ubiquitination, an E4 role for gp78 in Ub chain elongation? A, incubations were carried out as detailed under “Experimental Procedures,” and ubiquitinated CYP3A4 detected through Western immunoblotting analyses against HA-Ub and subsequent Typhoon scanning. B, PKA/PKC-mediated CYP3A4 phosphorylation enhances CYP3A4 ubiquitination by both E2-E3 complexes. Similar incubations in the presence of PKA/PKC for CYP3A4 phosphorylation were employed as in A. The color wheel intensity code is as shown.