1mhm

Crystal structure of S-adenosylmethionine decarboxylase from potato

spinqualitylabelsall models 1mhm, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1mhm is a 2 chain structure with sequence from Solanum tuberosum. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.3Å Ligands: PYR Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function DCAM_SOLTU Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed S-Adenosylmethionine decarboxylase has been implicated in cell growth and differentiation and is synthesized as a proenzyme, which undergoes autocatalytic cleavage to generate an active site pyruvoyl group. In mammals, S-adenosylmethionine decarboxylase is active as a dimer in which each protomer contains one alpha subunit and one beta subunit. In many higher organisms, autocatalysis and decarboxylation are stimulated by putrescine, which binds in a buried site containing numerous negatively charged residues. In contrast, plant S-adenosylmethionine decarboxylases are fully active in the absence of putrescine, with rapid autocatalysis that is not stimulated by putrescine. We have determined the structure of the S-adenosylmethionine decarboxylase from potato, Solanum tuberosum, to 2.3 A resolution. Unlike the previously determined human enzyme structure, the potato enzyme is a monomer in the crystal structure. Ultracentrifugation studies show that the potato enzyme is also a monomer under physiological conditions, with a weak self-association constant of 6.5 x 10(4) M(-)(1) for the monomer-dimer association. Although the potato enzyme contains most of the buried charged residues that make up the putrescine binding site in the human enzyme, there is no evidence for a putrescine binding site in the potato enzyme. Instead, several amino acid substitutions, including Leu13/Arg18, Phe111/Arg114, Asp174/Val181, and Phe285/His294 (human/potato), provide side chains that mimic the role of putrescine in the human enzyme. In the potato enzyme, the positively charged residues form an extensive network of hydrogen bonds bridging a cluster of highly conserved negatively charged residues and the active site, including interactions with the catalytic residues Glu16 and His249. The results explain the constitutively high activity of plant S-adenosylmethionine decarboxylases in the absence of putrescine and are consistent with previously proposed models for how putrescine together with the buried, negatively charged site regulates enzyme activity. Monomeric S-adenosylmethionine decarboxylase from plants provides an alternative to putrescine stimulation.,Bennett EM, Ekstrom JL, Pegg AE, Ealick SE Biochemistry. 2002 Dec 10;41(49):14509-17. PMID:12463749 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also SAM decarboxylase

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