May play an important role in cardiac antiarrhythmia via the strong suppression of voltage-gated L-type Ca(2+) currents. Regulates voltage-dependent L-type calcium channel subunit alpha-1C trafficking to the cell membrane. Inhibits cardiac hypertrophy through the calmodulin-dependent kinase II (CaMKII) pathway. Inhibits phosphorylation and activation of CAMK2D. Interacts with Calmodulin preferentially in the inactive, GDP-bound form. Interacts with CAMK2D (By similarity). Interacts with CACNB2. Interaction with CACNB2 regulates the trafficking of CACNA1C to the cell membrane. Mice show increased susceptibility to thoracic transverse aortic constriction (TAC)-induced cardiac hypertrophy. TAC-induced CAMKII phosphorylation in the heart is also significantly increased. Belongs to the small GTPase superfamily. RGK family.