Engineered Intermonomeric Disulfide Bonds in the Globular Domain of Newcastle Disease Virus Hemagglutinin-Neuraminidase Protein: Implications for the Mechanism of Fusion Promotion

Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Journal of Virology (Impact Factor: 4.44). 09/2008; 82(21):10386-96. DOI: 10.1128/JVI.00581-08
Source: PubMed


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.

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Available from: Thomas Musich, Apr 13, 2015
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    • "Based on the available structural information, it has emerged as an overarching concept that F triggering is initiated by receptor-induced changes on the attachment protein oligomer rather than the monomer level. Mahon and colleagues have pioneered a disulfide linking strategy for the NDV HN monomer-monomer interface (49), which has revealed that engineered disulfide bonds between two head monomers do not prevent membrane fusion. Rather, fusion activity was enhanced, arguing against a mechanism in which receptor binding affects the monomer-monomer interface within the head dimers. "
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    • "There have been an increasing number of studies supporting an important role for thiol (−SH)/disulfide (−S-S-) exchange in the entry of multiple viruses into susceptible cells, including Sindbis virus [1] , Baculovirus [2], Vaccinia virus [3], equine arteritis virus [4], Moloney murine leukemia virus [5], Newcastle disease virus [6-8], hepatitis delta virus [9] and HIV-1 (reviewed in [10,11]). "
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    • "These introduced disulfide bonds might somehow prevent the proper formation of MV-H tetramer or its conformational shift upon receptor binding (Saphire and Oldstone, 2011). The similar experiment with the NDV-HN protein did not affect its fusion-support activity (Mahon et al., 2008). "
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