Membrane fusion promoted by human metapneumovirus (HMPV) fusion (F) protein was suggested to require low pH (R. M. Schowalter, S. E. Smith, and R. E. Dutch, J. Virol. 80:10931-10941, 2006). Using prototype F proteins representing the four HMPV genetic lineages, we detected low-pH-dependent fusion only with some lineage A proteins and not with lineage B proteins. A glycine at position 294 was found responsible for the low-pH requirement in lineage A proteins. Only 6% of all HMPV lineage A F sequences have 294G, and none of the lineage B sequences have 294G. Thus, acidic pH is not a general trigger of HMPV F proteins for activity. Copyright,
Journal of Virology
Erasmus MC: University Medical Center Rotterdam

Herfst, S., Mas, V., Ver, L., Wierda, R., Osterhaus, A., Fouchier, R., & Melero, J. (2008). Low-pH-induced membrane fusion mediated by human metapneumovirus F protein is a rare, strain-dependent phenomenon. Journal of Virology, 82(17), 8891–8895. doi:10.1128/JVI.00472-08