The Ras superfamily of GTP binding proteins encompasses several gene families that regulate a plethora of events in the eukaryotic cell. Here we describe a novel branch of this superfamily which we have named RJLs. These are present in many unicellular organisms and also indeuterostomes but apparently missing in some intermediary phyla, suggesting an intriguing possibility of lateral gene transference between lower and higher eukaryotes. RJLs lack classical membrane targeting signals and the conserved glutamine residue that coordinates GTPhydrolysis in other proteins from the Ras superfamily. Interestingly, chordate orthologues are chimeras fused to J domains in their Cterminal, suggesting that these proteins recruit Hsc70 to specific sites in the cell. Expression analysis of RJLs from chordates suggestspredominant expression in nervous tissues, possibly reflecting a role for RJLs in the development or maintenance of the sophisticated chordate nervous system.