Protein which interacts with any form of the fat-soluble vitamin A. There are three active forms of vitamin A: retinol, retinal (retinaldehyde) and retinoic acid, which are all derived from the plant beta-carotene (provitamin A). Vitamin A is essential to night vision and is also required for epithelium differentiation, bone development, reproduction and the immune response. Symptoms associated with a deficiency of vitamin A are night blindness, changes in the eyes, poor bone development, weak tooth enamel and dry skin.