We report the primary characterization of a new gene KCNRG mapped at chromosome band 13q14.3. This gene includes three exons and has two alternatively spliced isoforms that are expressed in normal tissues and in some tumor cell lines. Protein KCNRG has high homology to tetramerization domain of voltage‐gated K⁺ channels. Using the patch‐clamp technique we determined that KCNRG suppresses K⁺ channel activity in human prostate cell line LNCaP. It is known that selective blockers of K⁺ channels suppress lymphocyte and LNCaP cell line proliferation. We suggest that KCNRG is a candidate for a B‐cell chronic lymphocytic leukemia and prostate cancer tumor suppressor gene.