Identification of a novel family of human Rab-like small GTP-binding proteins.

The presence of a novel family of Rab-like proteins (Rlp) in the human genome is reported. The gene encoding the Rlp-2 was isolated from a human lymphocyte genomic library. The Rlp-2 gene is intronless and was mapped to chromosome Xq21.3 using fluorescence in situ hybridization. Several cDNA clones encoding the Rlp-1 were identified in a human hippocampus lambda library. Northern analysis revealed a 2.1-kb transcript of Rlp-1 expressed predominantly in brain, heart and skeletal muscle. The transcript was also observed in all examined regions of the human brain at a similar level. An additional gene, termed Rlp-3, which is highly related to Rlp-1 and Rlp-2, was found in the GenBank Data Base. The predicted molecular mass for Rlp is approximately 31 kDa and is consistent with that of Rlp-1 synthesized in Escherichia coli.