Role of tryptophan 135 of Chandipura virus phosphoprotein P in dimerization and complex formation with leader RNA: structural aspect using time resolved anisotropy and simulation

The aggregation of phosphoprotein P of Chandipura virus (CHPV) and its interaction with viral leader (le) RNA in aqueous buffer and 40% ethylene glycol (EG)-buffer have been characterised using two single tryptophan (Trp/W) mutants W105F and W135F. The longer rotational correlation time [(θC)T] originating from overall motion observed at 300 nM concentration conforms to a globular structure of the monomer of WT and both the mutants. The (θC)T values also indicate that W135F does not form a dimer at 1500 nM concentration; while a dimer with disordered structure is predicted for both WT and W105F. The complexes of WT and W105F with le RNA at monomeric and dimeric conditions are indicated to have tight core packing. Dimerization and complex formation at both the concentrations enhance the correlation time arising from the localised motion of Trp side chain [(θC)S] for WT and W105F predicting hindered localized rotation of Trp 135. Comparative protein modelling and molecular dynamics (MD) simulations using the amino acids domain ranging from 105–168 of the full length CHPVP based on the vesicular stomatitis virus phosphoprotein (VSVP) also indicate that formation of dimers are more feasible for WT and W105F compared to W135F.