Interacts (when myristoylated) with UNC119 and UNC119B; interaction is required for localization to cilium. Localization to cilium is mediated via interaction with UNC119 and UNC119B, which bind to the myristoyl moiety of the N-terminus (By similarity). Expression is enriched in the ciliary axoneme. Expressed primarily in the kidney and liver. Expressed at lower levels in the lung, brain and heart. Expressed in the fetal kidney. Defects in Cys1 are a cause of polycystic kidney disease.