Co-chaperone required during oogenesis to repress transposable elements and prevent their mobilization, which is essential for the germline integrity. Acts via the piRNA metabolic process, which mediates the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and govern the methylation and subsequent repression of transposons. Acts as a co-chaperone via its interaction with Hsp83/HSP90 and is required for the biogenesis of all three piRNA major populations. Interacts with Hsp83. Present in the cytoplasm of germ cells. Component of the meiotic nuage, also named P granule, a germ-cell-specific organelle required to repress transposon activity during meiosis. Also present in Yb bodies. Strongly expressed in the germline stem cells and in 16-cell cysts. Present in the germ cells throughout embryogenesis. Defects are due to derepression of transposable elements and impaired piRNA biogenesis. Recessive female sterility with no effects on zygotic viability. Some strong alleles (WQ41 and WM40) also lead to male sterility. Belongs to the FKBP6 family. Although it contains a PPIase FKBP-type domain, does not show peptidyl-prolyl cis-trans isomerase activity.