The cation-dependent G-proteins: In a class of their own

► Sodium or potassium ions accelerate GTP hydrolysis by the cation-dependent G-proteins. ► Most cation-dependent GTPases select for potassium at their active sites. ► The cation-dependent GTPases are proposed as a new G-protein class. ► These GTPases exist in all three domains of life and are structurally unique. ► A list of predicted cation-dependent GTPases is presented.