Similarity: Belongs to the small GTPase superfamily. RGK family. subunit: Interacts with calmodulin preferentially to the inactive, GDP-form. Binds CAMKII which is capable of phosphorylating RAD in vitro. tissue specificity: Skeletal and cardiac muscle, and lung. Lesser amounts in placenta and kidney. Also detected in adipose tissue. Overexpressed in muscle of type II diabetic humans.