Enables Hsp90 protein binding activity. Acts upstream of or within chaperone-mediated protein folding. Located in cytosol. Is expressed in soleus and testis. Human ortholog(s) of this gene implicated in cataract 43 and myofibrillar myopathy. Orthologous to human UNC45B (unc-45 myosin chaperone B). [provided by Alliance of Genome Resources, Apr 2022]