title: Structural basis for allosteric regulation of human ribonucleotide reductase by nucleotide-induced oligomerization.
abstract: Ribonucleotide reductase (RR) is an α(n)β(n) (RR1-RR2) complex that maintains balanced dNTP pools by reducing NDPs to dNDPs. RR1 is the catalytic subunit, and RR2 houses the free radical required for catalysis. RR is allosterically regulated by its activator ATP and its inhibitor dATP, which regulate RR activity by inducing oligomerization of RR1. Here, we report the first X-ray structures of human RR1 bound to TTP alone, dATP alone, TTP-GDP, TTP-ATP, and TTP-dATP. These structures provide insights into regulation of RR by ATP or dATP. At physiological dATP concentrations, RR1 forms inactive hexamers. We determined the first X-ray structure of the RR1-dATP hexamer and used single-particle electron microscopy to visualize the α(6)-ββ'-dATP holocomplex. Site-directed mutagenesis and functional assays confirm that hexamerization is a prerequisite for inhibition by dATP. Our data indicate a mechanism for regulating RR activity by dATP-induced oligomerization.
authors.affiliation: Department of Biochemistry, University of Tennessee, Knoxville, TN, USA.
authors.forename: James Wesley
authors.initials: JW
authors.lastname: Fairman
authors.forename: Sanath Ranjan
authors.initials: SR
authors.lastname: Wijerathna
authors.forename: Md Faiz
authors.initials: MF
authors.lastname: Ahmad
authors.forename: Hai
authors.initials: H
authors.lastname: Xu
authors.forename: Ryo
authors.initials: R
authors.lastname: Nakano
authors.forename: Shalini
authors.initials: S
authors.lastname: Jha
authors.forename: Jay
authors.initials: J
authors.lastname: Prendergast
authors.forename: R Martin
authors.initials: RM
authors.lastname: Welin
authors.forename: Susanne
authors.initials: S
authors.lastname: Flodin
authors.forename: Annette
authors.initials: A
authors.lastname: Roos
authors.forename: Pär
authors.initials: P
authors.lastname: Nordlund
authors.forename: Zongli
authors.initials: Z
authors.lastname: Li
authors.forename: Thomas
authors.initials: T
authors.lastname: Walz
authors.forename: Chris Godfrey
authors.initials: CG
authors.lastname: Dealwis
mesh_terms: D000494:Allosteric Regulation; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003838:Deoxyadenine Nucleotides / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism*; D055503:Protein Multimerization; D012264:Ribonucleotide Reductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology*
chemical_list: D003838:Deoxyadenine Nucleotides; D009711:Nucleotides; D012264:Ribonucleotide Reductases; C026600:2'-deoxyadenosine triphosphate