title: The histone H4 tail regulates the conformation of the ATP-binding pocket in the SNF2h chromatin remodeling enzyme.
abstract: The chromatin remodeling complex ACF helps establish the appropriate nucleosome spacing for generating repressed chromatin states. ACF activity is stimulated by two defining features of the nucleosomal substrate: a basic patch on the histone H4 N-terminal tail and the specific length of flanking DNA. However, the mechanisms by which these two substrate cues function in the ACF remodeling reaction is not well understood. Using electron paramagnetic resonance spectroscopy with spin-labeled ATP analogs to probe the structure of the ATP active site under physiological solution conditions, we identify a closed state of the ATP-binding pocket that correlates with ATPase activity. We find that the H4 tail promotes pocket closure. We further show that ATPase stimulation by the H4 tail does not require a specific structure connecting the H4 tail and the globular domain. In the case of many DNA helicases, closure of the ATP-binding pocket is regulated by specific DNA substrates. Pocket closure by the H4 tail may analogously provide a mechanism to directly couple substrate recognition to activity. Surprisingly, the flanking DNA, which also stimulates ATP hydrolysis, does not promote pocket closure, suggesting that the H4 tail and flanking DNA may be recognized in different reaction steps.
authors.affiliation: Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA 94158, USA.
authors.forename: Lisa R
authors.initials: LR
authors.lastname: Racki
authors.affiliation: Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA 94158, USA.
authors.forename: Nariman
authors.initials: N
authors.lastname: Naber
authors.affiliation: Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA.
authors.forename: Ed
authors.initials: E
authors.lastname: Pate
authors.affiliation: Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA 94158, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Leonard
authors.affiliation: Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA 94158, USA.
authors.forename: Roger
authors.initials: R
authors.lastname: Cooke
authors.affiliation: Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, CA 94158, USA. Electronic address: geeta.narlikar@ucsf.edu.
authors.forename: Geeta J
authors.initials: GJ
authors.lastname: Narlikar
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D042002:Chromatin Assembly and Disassembly; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry*; D006657:Histones / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D061987:Sf9 Cells; D018411:Spodoptera
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D006657:Histones; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C409462:SMARCA5 protein, human
keywords: EPR spectroscopy; basic patch; human hACF; nucleosome; spin-labeled nucleotide