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1dgd

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{{STRUCTURE_1dgd| PDB=1dgd | SCENE= }}
{{STRUCTURE_1dgd| PDB=1dgd | SCENE= }}
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'''AN ALKALI METAL ION SIZE-DEPENDENT SWITCH IN THE ACTIVE SITE STRUCTURE OF DIALKYLGLYCINE DECARBOXYLASE'''
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===AN ALKALI METAL ION SIZE-DEPENDENT SWITCH IN THE ACTIVE SITE STRUCTURE OF DIALKYLGLYCINE DECARBOXYLASE===
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==Overview==
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The pyridoxal 5'-phosphate-dependent enzyme dialkylglycine decarboxylase (DGD) is activated by K+ and Rb+ ions, whereas Li+ and Na+ ions are inhibitory. A binding site for alkali metal ions close to the active site (site 1) was discovered in the crystal structure of DGD, and an exchange of K+ for Na+ at this site was shown to affect the conformation of two active site residues [Toney, M. D., Hohenester, E., Cowan, S. W., &amp; Jansonius, J. N. (1993) Science 261, 756-759]. We have investigated the effects of alkali metal ions on DGD activity and have determined the crystal structures at 2.8 A resolution of DGD with Li+ and Rb+ bound at site 1. Due to the weak scattering of the Li+ ion, its position had to be modeled using information from small molecule structures. A comparison of the DGD structures with Li+, Na+, K+, and Rb+ bound at site 1 reveals a striking correlation between active site structure and enzymatic activity. The small, inhibitory ions Li+ and Na+ are accommodated by replacing two protein-derived ligands of the larger, activating ions K+ and Rb+ by a single water molecule. This actuates a two-state structural switch between active and inactive enzyme that involves a concerted reorientation of the active site residues Ser80 and Tyr301 and a small change in the quaternary structure of the DGD tetramer. An important role of the essential K+ ion in both cofactor binding and the organization of a catalytically competent active site structure is proposed. In the structure of DGD with Rb+ bound at site 1, a second Rb+ ion has partially replaced the structural Na+ ion at metal binding site 2 on the surface of the DGD molecule, without significantly altering the protein structure. In contrast to Na+, the Rb+ ion is bound with unfavorable geometry, and it is proposed that the rigid site 2 structure results in a pronounced selectivity for Na+ ions.
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{{ABSTRACT_PUBMED_7947767}}
==About this Structure==
==About this Structure==
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[[Category: Jansonius, J N.]]
[[Category: Jansonius, J N.]]
[[Category: Lyase]]
[[Category: Lyase]]
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Revision as of 20:02, 30 June 2008

Image:1dgd.png

Template:STRUCTURE 1dgd

AN ALKALI METAL ION SIZE-DEPENDENT SWITCH IN THE ACTIVE SITE STRUCTURE OF DIALKYLGLYCINE DECARBOXYLASE

Template:ABSTRACT PUBMED 7947767

About this Structure

1DGD is a Single protein structure of sequence from Burkholderia cepacia. Full crystallographic information is available from OCA.

Reference

An alkali metal ion size-dependent switch in the active site structure of dialkylglycine decarboxylase., Hohenester E, Keller JW, Jansonius JN, Biochemistry. 1994 Nov 22;33(46):13561-70. PMID:7947767

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