This entry defines the C-terminal of various retinaldehyde/retinal-binding proteins that may befunctional components of the visual cycle. Cellular retinaldehyde-binding protein (CRALBP) carries 11-cis-retinol or 11-cis-retinaldehyde as endogenous ligands and may function as a substrate carrier protein that modulates interaction of these retinoids with visual cycle enzymes [<cite idref="PUB00006265"/>]. The multidomain protein Trio binds the LAR transmembrane tyrosine phosphatase, contains a protein kinase domain, and has separate rac-specific and rho-specific guanine nucleotide exchange factor domains [<cite idref="PUB00006347"/>]. Trio is a multifunctional protein that integrates and amplifies signals involved in coordinating actin remodeling, which is necessary for cell migration and growth.<p>Other members of the family are transfer proteins that include, guanine nucleotide exchange factor that may function as an effector of RAC1, phosphatidylinositol/phosphatidylcholine transfer protein that is required for the transport of secretory proteins from the golgicomplex and alpha-tocopherol transfer protein that enhances the transfer of the ligand between separate membranes.</p>