Open AccessBinding Affinity and Function of the Extremely Disordered Protein Complex Containing Human Linker Histone H1.0 and Its Chaperone ProTα
Author(s) -
Hanqiao Feng,
Bing-Rui Zhou,
Yawen Bai
Publication year - 2018
Publication title -
biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.43
H-Index - 253
eISSN - 1520-4995
pISSN - 0006-2960
DOI - 10.1021/acs.biochem.8b01075
Subject(s) - isothermal titration calorimetry , chaperone (clinical) , linker , histone h1 , chemistry , histone , dissociation constant , biophysics , linker dna , chromatin , crystallography , nucleosome , plasma protein binding , biochemistry , biology , dna , medicine , pathology , computer science , operating system , receptor
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 K D 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 K D 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.