The Ras family regulates a wide variety of cellular functions that include cell growth, differentiation, and apoptosis. In this study, we identified a novel human gene named RAP2C, isolated from human testis cDNA library, and mapped to Xq26.2 by searching the UCSC genomic database. The RAP2C cDNA contains an open reading frame of 552 bp, encoding a putative protein of 183 amino acid residues. The predicted protein contains a RAS domain. By RT-PCR analysis in various tissues, RAP2C was found to be principally expressed in the liver, skeletal muscle, prostate, uterus, rectum, stomach, and bladder and to a less extent in brain, kidney, pancreas, and bone marrow. RAP2C protein was located in cytoplasm when overexpressed in COS-7 cells. Reporter gene assays showed that overexpression of RAP2C in HEK293T cells activated the transcriptional activities of serum response element (SRE). These results indicate that RAP2C is a novel member of the Ras family, belonging to the Rap branch of small GTPase proteins and may be involved in SRE-mediated gene transcription.