The structure of a PKD domain from polycystin‐1: implications for polycystic kidney disease

Most cases of autosomal dominant polycystic kidney disease (ADPKD) are the result of mutations in the PKD1 gene. The PKD1 gene codes for a large cell‐surface glycoprotein, polycystin‐1, of unknown function, which, based on its predicted domain structure, may be involved in protein–protein and protein–carbohydrate interactions. Approximately 30% of polycystin‐1 consists of 16 copies of a novel protein module called the PKD domain. Here we show that this domain has a β‐sandwich fold. Although this fold is common to a number of cell‐surface modules, the PKD domain represents a distinct protein family. The tenth PKD domain of human and Fugu polycystin‐1 show extensive conservation of surface residues suggesting that this region could be a ligand‐binding site. This structure will allow the likely effects of missense mutations in a large part of the PKD1 gene to be determined.