Interaction of Dystrophin Rod Domain with Membrane Phospholipids

International audience; Dystrophin is assumed to act via the central rod domain as a flexible linker between the amino-terminal actin binding domain and carboxyl-terminal proteins associated with the membrane. The rod domain is made up of 24 spectrin-like repeats and has been shown to modify the physical properties of lipid membranes. The nature of this association still remains unclear. Trypto-phan residues tend to cluster at or near to the water-lipid interface of the membrane. To assess dystrophin rod domain-membrane interactions, tryptophan residues properties of two recombinant proteins of the rod domain were examined by 1 H NMR and fluorescence techniques in the presence of membrane lipids. F114 (residues 439-553) is a partly folded protein as inferred from 1 H NMR, tryptophan fluorescence emission intensity , and the excited state lifetime. By contrast, F125 (residues 439-564) is a folded compact protein. Trypto-phan fluorescence quenching shows that both proteins are characterized by structural fluctuations with their tryptophan residues only slightly buried from the surface. In the presence of negatively charged small vesi-cles, the fluorescence characteristics of F125 change dramatically, indicating that tryptophan residues are in a more hydrophobic environment. Interestingly, these modifications are not observed with F114. Fluorescence quenching experiments confirm that tryptophan residues are shielded from the solvent in the complex F125 lipids by a close contact with lipids. The use of membrane bound quenchers allowed us to conclude that dys-trophin rod domain lies along the membrane surface and may be involved in a structural array comprising membrane and cytoskeletal proteins as well as membrane lipids.