<p>This represents the N-terminal region of polycystin, a member of the Polycystin Cation Channel (PCC) family. Polycystin is a huge protein of 4303aa. Its repeated leucine-rich (LRR) segment is found in many proteins. It contains 16 polycystic kidney disease (PKD) domains, one LDL-receptor class A domain, one C-type lectin family domain, and 16-18 putative transmembrane regions in positions between residues 2200 and 4100. Polycystin-L has been shown to be a cation (Na<sup>+</sup>, K<sup>+</sup> and Ca<sup>2+</sup>) channel that is activated by Ca<sup>2+</sup>. Two members of the PCC family (polycystin 1 and 2) are mutated in autosomal dominant polycystic kidney disease, and polycystin-L is deleted in mice with renal and retinal defects [<cite idref="PUB00001323"/>, <cite idref="PUB00020131"/>].</p>