http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1978089/ (Supplementary material)
Cukkemane, A., Grüter, B., Novak, K., Genscher, T., Bönigk, W., Gerharz, T., et al. (2007). Subunits act independently in a cyclic nucleotide-activated K+ channel. EMBO Reports, 8, 749-755. doi: 10.1038/sj.embor.7401025.