The protein encoded by this gene is a calcium-binding protein that activates photoreceptor guanylate cyclases. This gene may have arisen due to a gene duplication event since there is a highly similar gene clustered with it on chromosome 6. Mutations in this gene can cause a form of retinitis pigmentosa. [provided by RefSeq, Nov 2009] see less The protein encoded by this gene is a calcium-binding protein that activates photoreceptor guanylate cyclases. This gene may have arisen due to a gene duplication event since there is a highly similar gene clustered with it on chromosome 6. Mutations in this gene can cause a form of retinitis pigmentosa. [provided by RefSeq, Nov 2009]