Structure of a Membrane-binding Domain from a Non-enveloped Animal Virus

Abstract

The ␥ 1 -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 ␥ 1 -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 ␥-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 ␥-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.

Infectious Bursal Disease Virus, a Non-enveloped Virus, Possesses a Capsid-associated Peptide That Deforms and Perforates Biological Membranes

“…4A). This structure is similar to that of the nodavirus membrane-active domain of the ␥ peptide (11). In the case of IBDV, the elbow between the two helices is generated by the presence of a proline, Pro 16 .…”

“…4, C and D show that the cis-isomerization of Pro 16 induces a reorientation of the second helix. In fact, the hydrophobic side of the second helix (16 -22) turns toward the hydrophobic side of the first helix (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) and the hydrophobic residues Phe 1 and Phe 3 . The trans to cis isomerization of Pro 16 results in the spatial clustering of hydrophobic residues of pep46 and thus may play an important role in membrane permeabilization.…”

“…Backbone atoms Heavy atoms (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) 0.41 Ϯ 0.18 1.49 Ϯ 0.44 (17)(18)(19)(20)(21)(22) 0.36 Ϯ 0.17 0.92 Ϯ 0.30 (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) 0.77 Ϯ 0.33 1.63 Ϯ 0.48 (18)(19)(20)(21)(22)(23)(24)(25)(26)(27) 0.87 Ϯ 0.39 1.14 Ϯ 0.40 (27)(28)(29)(30)…”

“…These critical substitutions are mainly present in the N-and C-terminal domains of pep46. Two of the four positively charged residues of the N-terminal domain (Lys 4 and Arg 11 ) cannot be substituted. Conversely, single substitutions of the negatively charged residues of the C-terminal domain allow virus amplification.…”

“…The ␥ peptide has the capacity to permeabilize biological membranes allowing genome translocation through the membrane (9,10). The recent determination of the atomic structure of the ␥ peptide membrane-active domain demonstrates similarities with the fusion peptides of glycoproteins of enveloped viruses: both are formed by a kinked helix (11). The ␥ peptide is located inside the capsid and is brought toward the membrane during entry.…”