1. Structure and mechanism of soybean ATP sulfurylase and the committed step in plant sulfur assimilation
- Author
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Samuel E. McKinney, Corey S. Westfall, Patrycja Baraniecka, Stanislav Kopriva, Soon Goo Lee, Geoffrey E. Ravilious, Joseph M. Jez, Jonathan Herrmann, Hari B. Krishnan, and Marco Giovannetti
- Subjects
Arabidopsis ,Enzyme Mechanisms ,Sequence Homology ,Plant Biology ,Crystallography, X-Ray ,Biochemistry ,Substrate Specificity ,chemistry.chemical_compound ,Adenosine Phosphosulfate ,Protein structure ,Adenosine Triphosphate ,Sulfur assimilation ,Catalytic Domain ,Site-Directed ,Sulfate assimilation ,Crystallography ,Plant Biochemistry ,food and beverages ,Enzyme Structure ,Plant ,Protein Structure ,Amino Acid Sequence ,Catalysis ,Haplotypes ,Hydrogen Bonding ,Kinetics ,Molecular Docking Simulation ,Molecular Sequence Data ,Mutagenesis, Site-Directed ,Mutation ,Protein Structure, Tertiary ,Sequence Homology, Amino Acid ,Soybeans ,Sulfate Adenylyltransferase ,Sulfur ,Enzyme structure ,Amino Acid ,Sulfate adenylyltransferase ,Biology ,Molecular Biology ,Active site ,Cell Biology ,chemistry ,Mutagenesis ,X-Ray ,biology.protein ,Adenosine triphosphate ,Tertiary - Abstract
Enzymes of the sulfur assimilation pathway are potential targets for improving nutrient content and environmental stress responses in plants. The committed step in this pathway is catalyzed by ATP sulfurylase, which synthesizes adenosine 5′-phosphosulfate (APS) from sulfate and ATP. To better understand the molecular basis of this energetically unfavorable reaction, the x-ray crystal structure of ATP sulfurylase isoform 1 from soybean (Glycine max ATP sulfurylase) in complex with APS was determined. This structure revealed several highly conserved substrate-binding motifs in the active site and a distinct dimerization interface compared with other ATP sulfurylases but was similar to mammalian 3′-phosphoadenosine 5′-phosphosulfate synthetase. Steady-state kinetic analysis of 20 G. max ATP sulfurylase point mutants suggests a reaction mechanism in which nucleophilic attack by sulfate on the α-phosphate of ATP involves transition state stabilization by Arg-248, Asn-249, His-255, and Arg-349. The structure and kinetic analysis suggest that ATP sulfurylase overcomes the energetic barrier of APS synthesis by distorting nucleotide structure and identifies critical residues for catalysis. Mutations that alter sulfate assimilation in Arabidopsis were mapped to the structure, which provides a molecular basis for understanding their effects on the sulfur assimilation pathway.
- Published
- 2014