FIG. 3.

Several models for the recruitment of Parkin to mitochondria by the kinase PINK1. In the direct binding model, PINK1 recruits Parkin through direct binding. In the direct phosphorylation model, phosphorylation of Parkin by PINK1 increases Parkin's affinity for depolarized mitochondria. In the shared substrate model, PINK1's phosphorylation of mitochondrial proteins increases their affinity for the E3 ubiquitin ligase Parkin. (To see this illustration in color the reader is referred to the web version of this article at www.liebertonline.com/ars).