RHOF (Rif) possesses an elevated intrinsic guanine nucleotide exchange activity (Jaiswal, Fansa et al. 2013). As GTP is more abundant in cells than GDP (Traut 1994), the exchange of guanine nucleotide on RHOF is spontaneous and insensitive to the presence of EDTA. RHOF is thought to be present in a constitutively active state (Jaiswal, Fansa et al. et al. 2013).