CatSper3, is a protein which in humans is encoded by the CATSPER3 gene. CatSper3 is a member of thecation channels of sperm family of proteins. The four proteins in this family together form a Ca2+-permeant ion channel specific essential for the correct function of sperm cells. Voltage-gated calcium channel that plays a central role in calcium-dependent physiological responses essential for successful fertilization, such as sperm hyperactivation, acrosome reaction and chemotaxis towards the oocyte.