Sperm-specific microtubule inner protein (MIP) part of the dynein-decorated doublet microtubules (DMTs) in flagellar axoneme. Forms an extensive interaction network in different conformations that reinforces the helix bundle composed by other tektin proteins (TEKT1 to TEKT4) and MIPs to anchor the tektin bundle onto the tubulin wall of A- tubule of the sperm flagellum. . This is the function of ENSG00000153060 (TEKT5, tektin 5).