Protein structural data was as follows: NP, PDB code 4QAZ ( Dziubańska et al., 2014 ); VP35, PDB code 3FKE ( Leung et al., 2009 ); GP, PDB code 3CSY ( Lee et al., 2008 ); VP30, PDB code 2I8B (... Hartlieb et al., 2007 ); VP24 PDB code 3VNE ( Zhang et al., 2012 ).