Search

Abstract: The previously identified membranotropic regions of the HCV E1 envelope glycoprotein, a class II membrane fusion protein, permitted us to identify different sequences which might be implicated in viral membrane fusion, membrane interaction and/or protein–protein binding. HCV E1 glycoprotein presents a membrano-active region immediately adjacent to the transmembrane segment, which could be involved in membrane destabilization similarly to the pre-transmembrane domains of class I fusion proteins. Consequently, we have carried out a study of the binding and interaction with the lipid bilayer of a peptide corresponding to segment 309–340, peptide E1PTM, as well as the structural changes which take place in both the peptide and the phospholipid molecules induced by the binding of the peptide to the membrane. Here we demonstrate that peptide E1PTM strongly partitions into phospholipid membranes, interacts with negatively-charged phospholipids and locates in a shallow position in the membrane. These data support its role in HCV-mediated membrane fusion and suggest that the mechanism of membrane fusion elicited by class I and II fusion proteins might be similar. [Copyright &y& Elsevier]

Abstract: Membrane fusion and fission underlie two limiting steps of enveloped virus replication cycle: access to the interior of the host-cell (entry) and dissemination of viral progeny after replication (budding), respectively. These dynamic processes proceed mediated by specialized proteins that disrupt and bend the lipid bilayer organization transiently and locally. We introduced Wimley–White membrane-water partitioning free energies of the amino acids as an algorithm for predicting functional domains that may transmit protein conformational energy into membranes. It was found that many viral products possess unusually extended, aromatic-rich pre-transmembrane stretches predicted to stably reside at the membrane interface. Here, we review structure–function studies, as well as data reported on the interaction of representative peptides with model membranes, all of which sustain a functional role for these domains in viral fusion and fission. Since pre-transmembrane sequences also constitute antigenic determinants in a membrane-bound state, we also describe some recent results on their recognition and blocking at membrane interface by neutralizing antibodies. [Copyright &y& Elsevier]

Cell infection by alphaviruses is accompanied by membrane permeability changes. New predictive approaches, including the computation of interfacial affinity and corresponding hydrophobic moments, suggest a segmented amphipathic-at-interface domain in the stem region of Semliki Forest virus fusion protein E1. Expression of E1 sequences in Escherichia coli cells confirmed that the membrane proximal plus transmembrane (TM) domain unit permeabilizes cells as efficiently as the 6K viroporin. Both our predictive and experimental data support the involvement of the E1 stem-TM region in membrane insertion and permeabilization. We propose to combine Wimley–White hydrophobicity analysis with expression-coupled permeability assays in order to identify viral products implied in breaching cell membrane barriers during infection. [Copyright &y& Elsevier]