Tektin 4, also known as TEKT4, is a 435 amino acid protein belonging to the tektin family. Localizing to cytoplasm as well as haploid round spermatids in testis, Tektin 4 is expressed in the abaxial surface of outer dense fibers (ORFs) in sperm flagella. Deletion of Tektin 4 is associated with uncoordinated waveform propagation and reduced velocity of sperm flagellum, resulting in subfertility.