CRAL-TRIO domain is a protein structural domain that binds small lipophilic molecules. [ 2 ] This domain is named after cellular retinaldehyde-binding protein (CRALBP) and TRIO guanine exchange factor. CRALB protein carries 11-cis- retinol or 11-cis-retinaldehyde. It modulates interaction of retinoids with visual cycle enzymes. TRIO is involved in coordinating actin