RGCs are Receptor Guanylate Cyclases that have an unusual structure: they are single-pass transmembrane receptors that have an active guanylate cyclase domain and a catalytically inactive kinase domain on the intracellular side. The guanylate cyclase domain makes the second messenger cGMP, and the kinase domain may have a regulatory role and may bind ATP (1,2).

Reference
1. Manning, G., Whyte, D.B., Martinez, R., Hunter, T. and Sudarsanam, S. (2002) The protein kinase complement of the human genome. Science, 298, 1912-1934. PMID: 12471243
2. Wikinome annotation:    Kinase Group RGC