title: Stimulation of Nipah Fusion: Small Intradomain Changes Trigger Extensive Interdomain Rearrangements.
abstract: Nipah is an emerging paramyxovirus that is of serious concern to human health. It invades host cells using two of its membrane proteins-G and F. G binds to host ephrins and this stimulates G to activate F. Upon activation, F mediates virus-host membrane fusion. Here we focus on mechanisms that underlie the stimulation of G by ephrins. Experiments show that G interacts with ephrin and F through separate sites located on two different domains, the receptor binding domain (RBD) and the F activation domain (FAD). No models explain this allosteric coupling. In fact, the analogous mechanisms in other paramyxoviruses also remain undetermined. The structural organization of G is such that allosteric coupling must involve at least one of the two interfaces-the RBD-FAD interface and/or the RBD-RBD interface. Here we examine using molecular dynamics the effect of ephrin binding on the RBD-RBD interface. We find that despite inducing small changes in individual RBDs, ephrin reorients the RBD-RBD interface extensively, and in a manner that will enhance solvent exposure of the FAD. While this finding supports a proposed model of G stimulation, we also find from additional simulations that ephrin induces a similar RBD-RBD reorientation in a stimulation-deficient G mutant, V209VG → AAA. Together, our simulations suggest that while inter-RBD reorientation may be important, it is not, by itself, a sufficient condition for G stimulation. Additionally, we find that the mutation affects the conformational ensemble of RBD globally, including the RBD-FAD interface, suggesting the latter's role in G stimulation. Because ephrin induces small changes in individual RBDs, a proper analysis of conformational ensembles required that they are compared directly-we employ a method we developed recently, which we now release at SimTK, and show that it also performs excellently for non-Gaussian distributions.
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Dutta
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida.
authors.forename: Ahnaf
authors.initials: A
authors.lastname: Siddiqui
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Botlani
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida. Electronic address: svarma@usf.edu.
authors.forename: Sameer
authors.initials: S
authors.lastname: Varma
mesh_terms: D036342:Ephrins / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D045405:Nipah Virus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D000072417:Protein Domains; D014763:Viral Matrix Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D053586:Virus Internalization
chemical_list: D036342:Ephrins; D014763:Viral Matrix Proteins