Reversible Inhibition of the Fusion Activity of Measles Virus F Protein by an Engineered Intersubunit Disulfide Bridge

Abstract
In search of target sites for the development of paramyxovirus inhibitors, we have engineered disulfide bridges to introduce covalent links into the prefusion F protein trimer of measles virus. F-Edm-452C/460C, predicted to bridge head and stalk domains of different F monomers, shows a high degree of proteolytic maturation and surface expression, predominantly as stable, dithiothreitol-sensitive trimers, but no fusion activity. Reduction of disulfide bridges partially restores activity. These findings underscore the importance of reversible intersubunit interactions between the stalk and head domains for F activity. Noncovalent small molecules mimicking this behavior may constitute a potent strategy for preventing paramyxovirus entry.