REM (Rad and Gem related GTP binding protein) is a member of the Rad/Gem/Kir subfamily of Ras-like GTPases and shares with other members of this subfamily some unusual structural features. Among these are nonconservative amino acid substitutions within guanine nucleotide binding and hydrolysis domains, unique effector domains, extended N- and C-termini, and a conserved C-terminal sequence thought to mediate membrane association but lacking a classical isoprenylation motif. REM, with a predicted molecular weight of 32.9 kDa, is most highly expressed in cardiac muscle and is expressed at more moderate levels in lung, kidney and skeletal muscle. REM is phosphorylated in vivo and has been shown to interact with several 14-3-3 isoforms. It has been reported that the GTP-bound form of a related Ras-like GTPase, GEM/kir, inhibits high-voltage activated Ca2+ channel activities by interacting directly with the ?subunit. The reduced channel activities are the result of a decreased a-subunit expression at the plasma membrane. This inhibition of L-type Ca2+ channels prevents Ca2+-triggered exocytosis in hormone-secreting cells. There are data that suggest that REM similarly regulates Ca2+ channel expression.