Specific salts effect is intensively studied from the prospective of modification of different physico-chemical properties of biomacromolecules. Limited knowledge of the specific salts effect on enzymes led us to address the influence of five sodium anions: sulfate, phosphate, chloride, bromide, and perchlorate, on catalytic and conformational properties of human rhinovirus-14 (HRV) 3C protease. The enzyme conformation was monitored by circular dichroism spectrum (CD) and by tyrosines fluorescence. Stability and flexibility of the enzyme have been analyzed by CD in the far-UV region, differential scanning calorimetry and molecular dynamics simulations, respectively. We showed significant influence of the anions on the enzyme properties in accordance with the Hofmeister effect. The HRV 3C protease in the presence of kosmotropic anions, in contrast with chaotropic anions, exhibits increased stability, rigidity. Correlations of stabilization effect of anions on the enzyme with their charge density and the rate constant of the enzyme with the viscosity B-coefficients of anions suggest direct interaction of the anions with HRV 3C protease. The role of stabilization and decreased fluctuation of the polypeptide chain of HRV 3C protease on its activation in the presence of kosmotropic anions is discussed within the frame of the macromolecular rate theory.

Centre for Interdisciplinary Biosciences P J Šafárik University in Košice Jesenná 5 04154 Košice Slovakia

Department of Biophysics Faculty of Science P J Šafárik University in Košice Jesenná 5 04154 Košice Slovakia

Department of Biophysics Institute of Experimental Physics Slovak Academy of Sciences Watsonova 47 040 01 Košice Slovakia

Faculty of Science University of South Bohemia in České Budějovice Branišovská 1645 31A 37005 České Budějovice Czech Republic

Laboratory of Structural Biology and Bioinformatics Institute of Microbiology of the Czech Academy of Sciences Zámek 136 37333 Nové Hrady Czech Republic

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