1j93

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{{STRUCTURE_1j93| PDB=1j93 | SCENE= }}
{{STRUCTURE_1j93| PDB=1j93 | SCENE= }}
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'''Crystal Structure and Substrate Binding Modeling of the Uroporphyrinogen-III Decarboxylase from Nicotiana tabacum: Implications for the Catalytic Mechanism'''
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===Crystal Structure and Substrate Binding Modeling of the Uroporphyrinogen-III Decarboxylase from Nicotiana tabacum: Implications for the Catalytic Mechanism===
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==Overview==
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The enzymatic catalysis of many biological processes of life is supported by the presence of cofactors and prosthetic groups originating from the common tetrapyrrole precursor uroporphyrinogen-III. Uroporphyrinogen-III decarboxylase catalyzes its conversion into coproporphyrinogen-III, leading in plants to chlorophyll and heme biosynthesis. Here we report the first crystal structure of a plant (Nicotiana tabacum) uroporphyrinogen-III decarboxylase, together with the molecular modeling of substrate binding in tobacco and human enzymes. Its structural comparison with the homologous human protein reveals a similar catalytic cleft with six invariant polar residues, Arg(32), Arg(36), Asp(82), Ser(214) (Thr in Escherichia coli), Tyr(159), and His(329) (tobacco numbering). The functional relationships obtained from the structural and modeling analyses of both enzymes allowed the proposal for a refined catalytic mechanism. Asp(82) and Tyr(159) seem to be the catalytic functional groups, whereas the other residues may serve in substrate recognition and binding, with Arg(32) steering its insertion. The crystallographic dimer appears to represent the protein dimer under physiological conditions. The dimeric arrangement offers a plausible mechanism at least for the first two (out of four) decarboxylation steps.
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(as it appears on PubMed at http://www.pubmed.gov), where 11524417 is the PubMed ID number.
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{{ABSTRACT_PUBMED_11524417}}
==About this Structure==
==About this Structure==
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[[Category: Crystallographic dimer]]
[[Category: Crystallographic dimer]]
[[Category: Plastidial enzyme]]
[[Category: Plastidial enzyme]]
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Revision as of 11:40, 1 July 2008

Image:1j93.png

Template:STRUCTURE 1j93

Crystal Structure and Substrate Binding Modeling of the Uroporphyrinogen-III Decarboxylase from Nicotiana tabacum: Implications for the Catalytic Mechanism

Template:ABSTRACT PUBMED 11524417

About this Structure

1J93 is a Single protein structure of sequence from Nicotiana tabacum. Full crystallographic information is available from OCA.

Reference

Crystal structure and substrate binding modeling of the uroporphyrinogen-III decarboxylase from Nicotiana tabacum. Implications for the catalytic mechanism., Martins BM, Grimm B, Mock HP, Huber R, Messerschmidt A, J Biol Chem. 2001 Nov 23;276(47):44108-16. Epub 2001 Aug 27. PMID:11524417

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