Highly glycosylated atypical beta-defensin involved in several aspects of sperm function. Facilitates sperm transport in the female reproductive tract and contributes to sperm protection against immunodetection; both functions are probably implicating the negative surface charge provided by its O-linked oligosaccharides in the sperm glycocalyx. Involved in binding of sperm to oviductal epithelial cells to form a sperm reservoir until ovulation. Release from the sperm surface during capacitation and ovaluation by an elevation of oviductal fluid pH is unmasking other surface components and allows sperm to penetrate the cumulus matrix and bind to the zona pellucida of the oocyte. In vitro has antimicrobial activity and may inhibit LPS-mediated inflammation (By similarity). Homodimer or homooligomer; disulfide-linked. Secreted by epididymal cells and is absorbed to the surface of sperm during transit through the epididymis. O-glycosylated; glycans contain alpha(2,3)-linked sialic acids (By similarity). Belongs to the beta-defensin family.