Biochemical and functional characterization of the ROC domain of DAPK establishes a new paradigm of GTP regulation in ROCO proteins.

DAPK (death-associated protein kinase) is a newly recognized member of the mammalian family of ROCO proteins, characterized by common ROC (Ras of complex proteins) and COR (C-terminal of ROC) domains. In the present paper, we review our recent work showing that DAPK is functionally a ROCO protein; its ROC domain binds and hydrolyses GTP. Furthermore, GTP binding regulates DAPK catalytic activity in a novel manner by enhancing autophosphorylation on inhibitory Ser308, thereby promoting the kinase 'off' state. This is a novel mechanism for in cis regulation of kinase activity by the distal ROC domain. The functional similarities between DAPK and the Parkinson's disease-associated protein LRRK2 (leucine-rich repeat protein kinase 2), another member of the ROCO family, are also discussed.