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| | {{STRUCTURE_1mhm| PDB=1mhm | SCENE= }} | | {{STRUCTURE_1mhm| PDB=1mhm | SCENE= }} |
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| - | '''Crystal structure of S-adenosylmethionine decarboxylase from potato'''
| + | ===Crystal structure of S-adenosylmethionine decarboxylase from potato=== |
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| - | ==Overview==
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| - | 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.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_12463749}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 12463749 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_12463749}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Pegg, A E.]] | | [[Category: Pegg, A E.]] |
| | [[Category: Covalent pyruvoyl group]] | | [[Category: Covalent pyruvoyl group]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 01:02:39 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jul 2 23:58:53 2008'' |
Revision as of 20:58, 2 July 2008
Template:STRUCTURE 1mhm
Crystal structure of S-adenosylmethionine decarboxylase from potato
Template:ABSTRACT PUBMED 12463749
About this Structure
1MHM is a Protein complex structure of sequences from Solanum tuberosum. Full crystallographic information is available from OCA.
Reference
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
Page seeded by OCA on Wed Jul 2 23:58:53 2008
