Salt bridge exchange binding mechanism between streptavidin and its DNA aptamer - Thermodynamics and spectroscopic evidences

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Title:	Salt bridge exchange binding mechanism between streptavidin and its DNA aptamer - Thermodynamics and spectroscopic evidences
Authors:	陳文逸;Kuo, Tai-Chih;Lee, Peng-Chen;Tsai, Ching-Wei;Chen, Wen-Yih
Contributors:	工學院化學工程與材料工程學系
Keywords:	aptamer;Aptamers, Nucleotide - chemistry;Aptamers, Nucleotide - genetics;Aptamers, Nucleotide - metabolism;Binding Sites;Calorimetry;circular dichroism;Dehydration;DNA - chemistry;DNA - genetics;DNA - metabolism;DNA-Binding Proteins - chemistry;DNA-Binding Proteins - genetics;DNA-Binding Proteins - metabolism;Enthalpy;Entropy;Ions;Ions - chemistry;Ions - metabolism;isothermal titration calorimetry;Nucleic Acid Conformation;Nucleic acids;Protein Binding;Salts;Sodium chloride;Sodium Chloride - chemistry;Sodium Chloride - metabolism;Spectroscopy;Spectrum Analysis - methods;streptavidin;Streptavidin - chemistry;Streptavidin - metabolism;Thermodynamics
Date:	2013-03-01
Issue Date:	2026-04-21 14:09:09 (UTC+8)
Publisher:	John Wiley and Sons Ltd;England: Blackwell Publishing Ltd
Abstract:	摘要： Protein‐nucleic acids binding driven by electrostatic interactions typically are characterized by the release of counter ions, and the salt‐inhibited binding association constant (Ka) and the magnitude of exothermic binding enthalpy (ΔH). Here, we report a non‐classical thermodynamics of streptavidin (SA)–aptamer binding in NaCl (140–350 mM) solutions near room temperatures (23–27 °C). By using isothermal titration calorimetry (ITC) and circular dichroism (CD)/fluorescence spectroscopy, we found that the binding was enthalpy driven with a large entropy cost (ΔH −20.58 kcal mol−1, TΔS −10.99 kcal mol−1, and Ka 1.08 × 107 M−1 at 140 mM NaCl 25 °C). With the raise of salt concentrations, the ΔH became more exothermic, yet the Ka was almost unchanged (ΔH −26.29 kcal mol−1 and Ka 1.50 × 107 M−1 at 350 mM NaCl 25 °C). The data suggest that no counter Na+ was released in the binding. Spectroscopy data suggest that the binding, with a stoichiometry of 2, was accompanied with substantial conformational changes on SA, and the changes were insensitive to the variation of salt concentrations. To account for the non‐classical results, we propose a salt bridge exchange model. The intramolecular binding‐site salt bridge(s) of the free SA and the charged phosphate group of aptamers re‐organize to form the binding complex by forming a new intermolecular salt bridge(s). The salt bridge exchange binding process requires minimum amount of counter ions releasing but dehydration of the contacting surface of SA and the aptamer. The energy required for dehydration is reduced in the case of binding solution with higher salt concentration and account for the higher binding exothermic mainly. Copyright © 2013 John Wiley & Sons, Ltd. Salt‐Bridge Exchange Model is proposed for the binding between Streptavidin with its aptamer. The binding model was proved by Isothermal Titration Calorimetry and Spectroscopic Methods. The Salt‐Bridge Exchange Model is a proved alternative binding mechanism for protein–aptamer association and provides fundamentals for the aptamer applications. 其他題名： J. Mol. Recognit 出版者： England: Blackwell Publishing Ltd 出版日期： 2013-03 出處： Journal of molecular recognition, 2013-03, Vol.26 (3), p.149-159 資源來源： Wiley Online Library - AutoHoldings Journals 版權： Copyright © 2013 John Wiley & Sons, Ltd. 識別號： ISSN: 0952-3499 識別號： ISSN: 1099-1352 識別號： EISSN: 1099-1352 識別號： DOI: 10.1002/jmr.2260 識別號： PMID: 23345105
Appears in Collections:	[Department of Chemical and Materials Engineering] journal & Dissertation

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