رابطه بین فعالیت Rnase A با فاصله بین Nε2-His12 وNδ1- His119 تحت اثر افزایش نمکهای پایدار کننده و ناپایدار کننده

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رابطه بین فعالیت Rnase A با فاصله بین Nε2-His12 وNδ1- His119 تحت اثر افزایش نمکهای پایدار کننده و ناپایدار کننده

Authors
Publisher
Springer Science+Business Media, Inc.
Keywords
  • Qu بیوشیمی

Abstract

The correlation of RNase A enzymatic activity with the changes in the distance between Nepsilon2-His12 and N delta1-His119 upon addition of stabilizing and destabilizing salts The Correlation of RNase A Enzymatic Activity with the Changes in the Distance between Ne2-His12 and Nd1-His119 Upon Addition of Stabilizing and Destabilizing Salts A. A. Moosavi-Movahedi,1,8 M. Gharanfoli,1,2 S. Jalili,3 F. Ahmad,4 J. Chamani,5 G. H. Hakimelahi,6 M. Sadeghi,7 M. Amani,1 and A. A. Saboury1 Received August 22, 2005 The effect of stabilizing and destabilizing salts on the catalytic behavior of ribonuclease A (RNase A) was investigated at pH 7.5 and 25°C, using spectrophotometric, viscometric and molecular dynamic methods. The changes in the distance between Ne2 of His12 and Nd1 of His119 at the catalytic center of RNase A upon the addition of sodium sulfate, sodium hydrogen sulfate and sodium thiocyanate were evaluated by molecular dynamic methods. The compactness and expansion in terms of Stokes radius of RNase A upon the addition of sulfate ions as kosmotropic salts, and thiocyanate ion as a chaotropic salt, were estimated by viscometric measurements. Enzyme activity was measured using cytidine 2¢, 3¢-cyclic mono- phosphate as a substrate. The results from the measurements of distances between Ne2 of His12 and Nd1of His119 and Stokes radius suggest (i) that the presence of sulfate ions decreases the distance between the catalytic His residues and increases the globular compactness, and (ii) that there is an expansion of the enzyme surface as well as elongation of the catalytic center in the presence of thiocyanate ion. These findings are in agreement with activity measurements. KEY WORDS: catalytic activity; distance calculation; folding/unfolding; molecular dynamics; RNase A; sulfate ions; thiocyanate ion. 1. INTRODUCTION Bovine pancreatic ribonuclease A (RNase A) cata- lyzes the cleavage of polyribonuleotides through a transphorolytic step generating a te

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