The invention provides isolated nucleic acid and amino acid sequences of CNG3B, antibodies to CNG3B, methods of detecting CNG3B, and methods of screening for modulators of cyclic nucleotide-gated ion channels using biologically active CNG3B. The invention further provides, in a computer system, a method of screening for mutations of human CNG3B genes as well as a method for identifying a three-dimensional structure of human CNG3B polypeptides.