RLBP1, as known as retinaldehyde binding protein 1, is a soluble protein. It participates in the regeneration of active 11-cis-retinol and 11-cis-retinaldehyde, from the inactive 11-trans products of the rhodopsin photocycle and in the de novo synthesis of these retinoids from 11-trans metabolic precursors. The cycling of retinoids between photoreceptor and adjacent pigment epithelium cells is known as the 'visual cycle'. Recombinant human RLBP1, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.