Engineered intermonomeric disulfide bonds in the globular domain of Newcastle disease virus hemagglutinin-neuraminidase protein: implications for the mechanism of fusion promotion.
ABSTRACT The promotion of membrane fusion by Newcastle disease virus (NDV) requires an interaction between the viral hemagglutinin-neuraminidase (HN) and fusion (F) proteins, although the mechanism by which this interaction regulates fusion is not clear. The NDV HN protein exists as a tetramer composed of a pair of dimers. Based on X-ray crystallographic studies of the NDV HN globular domain (S. Crennell et al., Nat. Struct. Biol. 7:1068-1074, 2000), it was proposed that the protein undergoes a significant conformational change from an initial structure having minimal intermonomeric contacts to a structure with a much more extensive dimer interface. This conformational change was predicted to be integral to fusion promotion with the minimal interface form required to maintain F in its prefusion state until HN binds receptors. However, no evidence for such a conformational change exists for any other paramyxovirus attachment protein. To test the NDV model, we have engineered a pair of intermonomeric disulfide bonds across the dimer interface in the globular domain of an otherwise non-disulfide-linked NDV HN protein by the introduction of cysteine substitutions for residues T216 and D230. The disulfide-linked dimer is formed both intracellularly and in the absence of receptor binding and is efficiently expressed at the cell surface. The disulfide bonds preclude formation of the minimal interface form of the protein and yet enhance both receptor-binding activity at 37 degrees C and fusion promotion. These results confirm that neither the minimal interface form of HN nor the proposed drastic conformational change in the protein is required for fusion.
[Show abstract] [Hide abstract]
ABSTRACT: The Paramyxoviridae family includes many viruses that are pathogenic in humans, including parainfluenza viruses, measles virus, respiratory syncytial virus, and the emerging zoonotic Henipaviruses. No effective treatments are currently available for these viruses, and there is a need for efficient antiviral therapies. Paramyxoviruses enter the target cell by binding to a cell surface receptor and then fusing the viral envelope with the target cell membrane, allowing the release of the viral genome into the cytoplasm. Blockage of these crucial steps prevents infection and disease. Binding and fusion are driven by two virus-encoded glycoproteins, the receptor-binding protein and the fusion protein, that together form the viral "fusion machinery." The development of efficient antiviral drugs requires a deeper understanding of the mechanism of action of the Paramyxoviridae fusion machinery, which is still controversial. Here, we review recent structural and functional data on these proteins and the current understanding of the mechanism of the paramyxovirus cell entry process. © 2015 Elsevier Inc. All rights reserved.Progress in molecular biology and translational science 129C:1-32. DOI:10.1016/bs.pmbts.2014.10.001 · 3.11 Impact Factor
Conference Paper: 2.8 μm Er,Cr:YSGG laser beam hollow waveguide transmission[Show abstract] [Hide abstract]
ABSTRACT: Er,Cr:YScGG is an important laser material for medical applications in the mid-infrared because of the strong absorption of its 2794 nm line in water. This wavelength has been demonstrated to have reasonably high transmission in hollow glass waveguides, making a practical and convenient delivery system for the beam. These waveguides, however, are sensitive to mode quality and have been tested only with low power TEMoo lasers. We decided, therefore, to examine the transmission of these waveguides when the laser runs at high power (up to 12 W) and multimode, but with some effort to minimize M2 without undue compromise in powerLasers and Electro-Optics Society Annual Meeting, 1995. 8th Annual Meeting Conference Proceedings, Volume 1., IEEE; 01/1995
[Show abstract] [Hide abstract]
ABSTRACT: The fusion of Nipah with host cells is facilitated by two of their glycoproteins, the G and the F proteins. The binding of cellular ephrins to the G head domain causes the G stalk domain to interact differently with F, which activates F to mediate virus-host fusion. To gain insight into how the ephrin binding signal transduces from the head to the stalk domain of G, we examine quantitatively the differences between the conformational ensembles of the G head domain in its ephrin-bound and unbound states. We consider the human ephrins B2 and B3, and a double mutant of B2, all of which trigger fusion. The ensembles are generated using molecular dynamics, and the differences between them are quantified using a new machine learning method. We find that the portion of the G head domain whose conformational density is altered equivalently by the three ephrins is large, and comprises of ~25% of the residues in the G head domain. This subspace also includes the residues that are known to be important to F activation, which suggests that it contains at least one common signaling pathway. The spatial distribution of the residues constituting this subspace supports the model of signal transduction in which the signal transduces via the G head dimer interface. This study also adds to the growing list of examples where signaling does not depend solely on backbone deviations. In general, this study provides an approach to filter out conserved patterns in protein dynamics. © Proteins 2014;. © 2014 Wiley Periodicals, Inc.Proteins Structure Function and Bioinformatics 12/2014; 82(12). DOI:10.1002/prot.24541 · 2.92 Impact Factor