CGREF1, also known as CGR11, is predicted to enable calcium ion binding activity and to be involved in negative regulation of cell population proliferation. Human GREF1 protein has 4 clustered 17-amino acid repeats within the C terminus, suggesting a structure resembling 4 alpha-helical domains interrupted by distinct turns. Northern blot analysis of rat tissues demonstrated expression of CGR11 predominantly in the whole brain and kidney, with limited expression in heart, lung, liver, and skeletal muscle and no expression in spleen and testis.