CALR3 capacity for calcium-binding may be absent or much lower than that of CALR (By similarity). During spermatogenesis, may act as a lectin-independent chaperone for specific client proteins such as ADAM3. Required for sperm fertility. Component of an EIF2 complex at least composed of CELF1/CUGBP1, CALR, CALR3, EIF2S1, EIF2S2, HSP90B1 and HSPA5. Testis specific, absent in mature sperm. Defective sperm migration from the uterus into the oviduct and defective binding to the zona pellucida. Belongs to the calreticulin family.