Aggregates of an amphiphilic synthetic peptide bind and deliver all-trans retinol and all-trans retinoic acid into fibroblast cells

The structure and conformational behaviour of a vector peptide, designed by association of a fusion peptide and a nuclear localization sequence, are described. A beta-sheet domain is observed in which fluorescence measurements show that ten peptide molecules bind one all-trans retinol or all-trans retinoic acid molecule with a strong affinity (K'(d) = 40 nM). Stoichiometry and affinity of the binding can be compared with those of cellular retinoid binding proteins, the structure of which is an anti-parallel beta barrel. Analogy between the system under study and cellular retinoid-binding proteins is discussed. Peptide-helped inter nalization and subsequent perinuclear localization of retinol in human fibroblast cells confirm this analogy. Also, this last result shows that the peptide is an efficient carrier for insoluble substances like retinoids.