Diverse regulatory mechanisms of StARkin domains in land plants and mammals.

The StARkin domain (derived from 'kin of steroidogenic acute regulatory protein (StAR)') is an evolutionarily conserved helix-grip-fold structure. StARkin domains possess a deep hydrophobic pocket capable of binding lipophilic ligands such as fatty acids, sterols, and isoprenoids. Dysregulation of StARkin proteins has profound effects on disease and development. In this review, we profile recent mechanistic and evolutionary studies, which highlight the remarkable diversity of regulatory mechanisms employed by the StARkin module. Although primarily focused on land plants, we also discuss select key advances in mammalian StARkin biology. The diversity of perspectives, systems, and approaches described here may be helpful to researchers characterizing poorly understood StARkin proteins.