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Updated: Feb 2, 2026

In Vitro Characterization of Histone Chaperones using Analytical, Pull-Down and Chaperoning Assays
Published on: December 29, 2021
Binding Affinity and Function of the Extremely Disordered Protein Complex Containing Human Linker Histone H1.0 and
Hanqiao Feng1, Bing-Rui Zhou1, Yawen Bai1
1Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Bethesda , Maryland 20892 , United States.
None:
It was recently reported that human linker histone H1.0 and its chaperone prothymosin-α (ProTα) form an extremely disordered 1:1 complex with an ultrahigh affinity (equilibrium dissociation constant KD of ∼2 × 10-12 M) measured using a single-molecule Förster resonance energy transfer method. It was hypothesized that the ultrahigh affinity and extreme disorder may be required for the chaperone function of ProTα, in which it displaces the linker histone from condensed chromatin. Here, we measure the binding affinity for the ProTα-H1.0 complex using isothermal titration calorimetry and report a KD value of (4.6 ± 0.5) × 10-7 M. In addition, we show that ProTα facilitates the formation of the H1.0-nucleosome complex in vitro. The results of our study contrast with those of the previous report and provide new insights into the chaperone function of ProTα. Possible causes for the observed discrepancy in binding affinity are discussed.
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