Structure of a Membrane-binding Domain from a Non-enveloped Animal Virus: INSIGHTS INTO THE MECHANISM OF MEMBRANE PERMEABILITY AND CELLULAR ENTRY

• Published in: The Journal of biological chemistry 2006-09, Vol.281 (39), p.29278-29286
• Main Authors: Maia, Lenize F, Soares, Márcia R, Valente, Ana P, Almeida, Fabio C.L, Oliveira, Andréa C, Gomes, Andre M.O, Freitas, Monica S, Schneemann, Anette, Johnson, John E, Silva, Jerson L
• Format: Article
• Language: English
• Subjects: Animals; Cell Membrane - virology; Cell Membrane Permeability; Circular Dichroism; Flock house virus; Hydrogen-Ion Concentration; Lipids - chemistry; Liposomes - chemistry; Membrane Fusion; Molecular Conformation; Nodavirus; Peptides - chemistry; Protein Conformation; Protein Structure, Secondary; Sodium Dodecyl Sulfate - chemistry; Trifluoroethanol - chemistry
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M604689200

The γ1-peptide is a 21-residue lipid-binding domain from the non-enveloped Flock House virus (FHV). Unlike enveloped viruses, the entry of non-enveloped viruses into cells is believed to occur without membrane fusion. In this study, we performed NMR experiments to establish the solution structure of a membrane-binding peptide from a small non-enveloped icosahedral virus. The three-dimensional structure of the FHV γ1-domain was determined at pH 6.5 and 4.0 in a hydrophobic environment. The secondary and tertiary structures were evaluated in the context of the capacity of the peptide for permeabilizing membrane vesicles of different lipid composition, as measured by fluorescence assays. At both pH values, the peptide has a kinked structure, similar to the fusion domain from the enveloped viruses. The secondary structure was similar in three different hydrophobic environments as follows: water/trifluoroethanol, SDS, and membrane vesicles of different compositions. The ability of the peptide to induce vesicle leakage was highly dependent on the membrane composition. Although the γ-peptide shares some structural properties to fusion domains of enveloped viruses, it did not induce membrane fusion. Our results suggest that small protein components such as the γ-peptide in nodaviruses (such as FHV) and VP4 in picornaviruses have a crucial role in conducting nucleic acids through cellular membranes and that their structures resemble the fusion domains of membrane proteins from enveloped viruses.