XRP2, also known as Protein XRP2 and RP2, is a member of the TBCC (tubulin cofactor C) family and contains one C-CAP/cofactor C-like domain. This protein is encoded by the RP2 gene in humans. XRP2 stimulates the GTPase activity of tubulin, but does not enhance tubulin heterodimerization. XRP2 acts as guanine nucleotide dissociation inhibitor for ARL3. Defects in RP2 gene are the cause of retinitis pigmentosa type 2 (RP2), also known as X-linked retinitis pigmentosa 2 (XLRP-2). It leads to degeneration of retinal photoreceptor cells. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well.