The Ras superfamily is a protein superfamily of small GTPases .  Members of the superfamily are divided into families and subfamilies based on their structure, sequence and function. The five main families are Ras, Rho , Ran , Rab and Arf GTPases.  The Ras family itself is further divided into 6 subfamilies: Ras , Ral , Rap , Rheb , Rad and Rit. Miro is a recent contributor to the superfamily. Each subfamily shares the common core G domain, which provides essential GTPase and nucleotide exchange activity.