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Updated: Aug 23, 2026

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo
Published on: October 23, 2016
Detection and characterization of an acid-induced folding intermediate of endostatin
Xiaoyu Wu1, Jing Huang, Guodong Chang
1Department of Biological Sciences and Biotechnology, MOE laboratory of Protein Science, Tsinghua University, Beijing 100084, PR China.
Abstract:
Endostatin, an important angiogenesis inhibitor, is very acid resistant. We are particularly interested in knowing that whether or not endostatin can form a folding intermediate during acid titration. 1H-NMR, CD spectrum, and ANS binding assay show that endostatin at pH 2.0 contains little tertiary structure, but retains substantial secondary structure with strong ANS binding, and Na2SO4 or TFE is found to strongly stabilize endostatin at pH 2.0. All these observations are consistent with the formation of a folding intermediate at pH 2.0. Kinetics studies show that sulfate anions significantly slow down the process for endostatin to reach its equilibrium state at pH 2.0. A regular increase in the amount of alpha-helix content of the intermediate of endostatin at pH 2.0 is found when the concentration of TFE is increased in the range of 0-40%, suggesting that endostatin has an intrinsic alpha-helical propensity.
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