Thermodynamics analysis of salt concentration effects on the interaction between dengue virus NS3 helicase and ss RNA

AV GAMARNIK; JJ INCICCO; LG GEBHARD; LA CABABIE; SB. KAUFMAN; RM. GONZÁLEZ LEBRERO

Conferencia; EMBO Conference. Helicases and nucleic acid-based machines: Structure, mechanism and regulation and roles in human disease; 2017

p { margin-bottom: 0.21cm; }Denguevirus NS3 protein (DENV) is a helicase that catalyzes the hydrolysisof ATP and couples the free energy of this reaction to thetranslocationon single-strandedand unwinddouble-strandedofRNA.Most protein-nucleic acid interactions are extremely sensitive to thesalconcentrationpresent in solution. This is because linear nucleic acids are highlycharged polyanions and therefore capture cations in their vicinitythus reducing their net charge. Numerous studies indicate that theeffects of cations, anions, pH and temperature are thermodynamicallycoupled. Therefore, to determine the effect/s exerted by any of thesevariables, it is necessary to know in detail how the others variablesoperateand this information is essential to elucidate the multiple bindingequilibria involved in the NS3/RNA interaction. We present results ofstudies of the effect of different cations (K+,Na+and Rb+)on the NS3/ssRNAinteraction. Applying Manning´s theory [1] we determined that 10ionic interactions are involved in the binding process. In addition,we studied the effect of temperature on the NS3/RNA interaction anddetermined the enthalpic and entropic contributions to the Gibbs freeenergy associated with the effect of salts on the NS3/RNAequilibrium.Ourresultsindicate that association of NS3 to ssRNAis predominantly enthalpic and the changes in ΔrGºobs,due to the increase in salt concentration are entirelyexplainedby the variation of the entropic contribution which, it was observed,is linear with log [K+].