On the mechanisms of bananin activity against severe acute respiratory syndrome coronavirus.

In a previous study, severe acute respiratory syndrome coronavirus (SARS-CoV) was cultured in the presence of bananin, an effective adamantane-related molecule with antiviral activity. In the present study, we show that all bananin-resistant variants exhibit mutations in helicase and membrane protein, although no evidence of bananin interference on their mutual interaction has been found. A structural analysis on protein sequence mutations found in SARS-CoV bananin-resistant variants was performed. The S259/L mutation of SARS-CoV helicase is always found in all the identified bananin-resistant variants, suggesting a primary role of this mutation site for bananin activity. From a structural analysis of SARS-CoV predicted helicase structure, S259 is found in a hydrophilic surface pocket, far from the enzyme active sites and outside the helicase dimer interface. The S/L substitution causes a pocket volume reduction that weakens the interaction between bananin and SARS-CoV mutated helicase, suggesting a possible mechanism for bananin antiviral activity.