title: Inhibition of yeast ribonucleotide reductase by Sml1 depends on the allosteric state of the enzyme.
abstract: Sml1 is an intrinsically disordered protein inhibitor of Saccharomyces cerevisiae ribonucleotide reductase (ScRR1), but its inhibition mechanism is poorly understood. RR reduces ribonucleoside diphosphates to their deoxy forms, and balances the nucleotide pool. Multiple turnover kinetics show that Sml1 inhibition of dGTP/ADP- and ATP/CDP-bound ScRR follows a mixed inhibition mechanism. However, Sml1 cooperatively binds to the ES complex in the dGTP/ADP form, whereas with ATP/CDP, Sml1 binds weakly and noncooperatively. Gel filtration and mutagenesis studies indicate that Sml1 does not alter the oligomerization equilibrium and the CXXC motif is not involved in the inhibition. The data suggest that Sml1 is an allosteric inhibitor.
authors.affiliation: Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Tessianna A
authors.initials: TA
authors.lastname: Misko
authors.affiliation: Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Sanath R
authors.initials: SR
authors.lastname: Wijerathna
authors.affiliation: Department of Quantitative Health Sciences, Cleveland Clinic Foundation, OH, USA.
authors.forename: Tomas
authors.initials: T
authors.lastname: Radivoyevitch
authors.affiliation: Department of Chemistry, Cleveland State University, OH, USA.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Berdis
authors.affiliation: Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Md Faiz
authors.initials: MF
authors.lastname: Ahmad
authors.affiliation: Department of Biochemistry, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Harris
authors.affiliation: Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Chris G
authors.initials: CG
authors.lastname: Dealwis
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology; D020816:Amino Acid Motifs; D011485:Protein Binding / Q000502:physiology; D055503:Protein Multimerization / Q000502:physiology; D012264:Ribonucleotide Reductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C115052:SML1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D012264:Ribonucleotide Reductases; C551024:Rnr1 protein, S cerevisiae
keywords: enzyme kinetics; intrinsically disordered protein; mixed inhibition; nucleotides; oligomerization