Functions as part of axonemal radial spoke complexes that play an important part in the motility of sperm and cilia. Does not seem to have nucleoside diphosphate kinase (NDPK) activity (PubMed:9742940). Confers protection from cell death by BAX and alters the cellular levels of several antioxidant enzymes including GPX5. May play a role in spermiogenesis by increasing the ability of late-stage spermatids to eliminate reactive oxygen species (By similarity). Exhibits a 3′-5′ exonuclease activity with a preference for single-stranded DNA, suggesting roles in DNA proofreading and repair (PubMed:16313181).