This domain represents the polycystin domain from group II of Transient receptor potential (TRP) channels (TRPP) including PKD1, PKD2, PKD2L and mucolipins. The polycystin domain display a sandwich-like shape with five beta-sheets in the tilted middle layer, three alpha-helices on one side and a large loop with two short antiparallel beta-sheets on the other [3].

1: Polycystin-L is a calcium-regulated cation channel permeable to calcium ions. Chen XZ, Vassilev PM, Basora N, Peng JB, Nomura H, Segal Y, Brown EM, Reeders ST, Hediger MA, Zhou J; Nature 1999;401:383-386. PMID:10517637

2: Polycystin-2 is a novel cation channel implicated in defective intracellular Ca(2+) homeostasis in polycystic kidney disease. Vassilev PM, Guo L, Chen XZ, Segal Y, Peng JB, Basora N, Babakhanlou H, Cruger G, Kanazirska M, Ye Cp, Brown EM, Hediger MA, Zhou J; Biochem Biophys Res Commun 2001;282:341-350. PMID:11264013

3: Cryo-EM structure of the polycystic kidney disease-like channel PKD2L1. Su Q, Hu F, Liu Y, Ge X, Mei C, Yu S, Shen A, Zhou Q, Yan C, Lei J, Zhang Y, Liu X, Wang T; Nat Commun. 2018;9:1192. PMID:29567962