Apg16p mediates Apg5p assembly. Immunoprecipitation was carried out as described in Figure 3, using apg12Δ (YNM107) and apg12Δapg16Δ cells (YNM115) carrying pMyc‐APG12 (CEN) and pHA‐APG5 (CEN) (B). Following SDS-PAGE, immunoprecipitates were subjected to immunoblot analysis using anti‐HA or anti‐Myc antibody as indicated. A model of the Apg12p-Apg5p-Apg16p complex is illustrated in each panel. Apg16p forms a homo‐oligomer through its C‐terminal coiled‐coil region. It is not clear whether Apg16p forms a dimer or a larger multimer. The N‐terminal region of each Apg16p interacts with Apg5p; most of these complexes are conjugated to Apg12p (A) but a small population are unmodified (B). In the absence of Apg16p, separate Apg5ps do not assemble. 