Here we report the molecular cloning and biochemical characterization of Re
m2 (for Rem, Rad and Gem-related 2), a novel GTP-binding protein identified
on the basis of its homology with the Rem, Rad, Gem and Kir (RGK) family o
f Ras-related small GTP-binding proteins. Rem2 mRNA was detected in rat bra
in and kidney, making it the first member of the RGK family to be expressed
at relatively high levels in neuronal tissues. Recombinant Rem2 binds GTP
saturably and exhibits a low intrinsic rate of GTP hydrolysis. Surprisingly
, the guanine nucleotide dissociation constants for both Rem2 and Rem are s
ignificantly different than the majority of the Ras-related GTPases, displa
ying higher dissociation rates for GTP than GDP. Localization studies with
green fluorescent protein (GFP)-tagged recombinant protein fusions indicate
that Rem2 has a punctate, plasma membrane localization. Deletion of the C-
terminal seven amino acid residues that are conserved in all RGK family mem
bers did not affect the cellular distribution of the GFP fusion protein, wh
ereas a larger deletion, including much of the polybasic region of the Rem2
C-terminus, resulted in its redistribution to the cytosol. Thus Rem2 is a
GTPase of the RGK family with distinctive biochemical properties and posses
sing a novel cellular localization signal, consistent with its having a uni
que role in cell physiology.