This gene encodes a member of the heat shock protein 40 co-chaperone family which is produced in large amounts in the testis and is located on the radial spokes of the axoneme in human sperm flagella and other flagellar structures. The encoded protein associates with the sperm annulus, as part of the septin complex, through direct interaction with septin 4, during sperm terminal differentiation. Naturally occurring mutations in this gene are associated with primary ciliary dyskinesia and male infertility. [provided by RefSeq, Apr 2017].