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1qrm

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[[Image:1qrm.gif|left|200px]]
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{{STRUCTURE_1qrm| PDB=1qrm | SCENE= }}
{{STRUCTURE_1qrm| PDB=1qrm | SCENE= }}
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'''A CLOSER LOOK AT THE ACTIVE SITE OF GAMMA-CARBONIC ANHYDRASES: HIGH RESOLUTION CRYSTAL STRUCTURES OF THE CARBONIC ANHYDRASE FROM METHANOSARCINA THERMOPHILA'''
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===A CLOSER LOOK AT THE ACTIVE SITE OF GAMMA-CARBONIC ANHYDRASES: HIGH RESOLUTION CRYSTAL STRUCTURES OF THE CARBONIC ANHYDRASE FROM METHANOSARCINA THERMOPHILA===
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==Overview==
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The prototype of the gamma-class of carbonic anhydrase has been characterized from the methanogenic archaeon Methanosarcina thermophila. Previously reported kinetic studies of the gamma-class carbonic anhydrase are consistent with this enzyme having a reaction mechanism similar to that of the mammalian alpha-class carbonic anhydrase. However, the overall folds of these two enzymes are dissimilar, and apart from the zinc-coordinating histidines, the active site residues bear little resemblance to one another. The crystal structures of zinc-containing and cobalt-substituted gamma-class carbonic anhydrases from M. thermophila are reported here between 1.46 and 1.95 A resolution in the unbound form and cocrystallized with either SO(4)(2)(-) or HCO(3)(-). Relative to the tetrahedral coordination geometry seen at the active site in the alpha-class of carbonic anhydrases, the active site of the gamma-class enzyme contains additional metal-bound water ligands, so the overall coordination geometry is trigonal bipyramidal for the zinc-containing enzyme and octahedral for the cobalt-substituted enzyme. Ligands bound to the active site all make contacts with the side chain of Glu 62 in manners that suggest the side chain is likely protonated. In the uncomplexed zinc-containing enzyme, the side chains of Glu 62 and Glu 84 appear to share a proton; additionally, Glu 84 exhibits multiple conformations. This suggests that Glu 84 may act as a proton shuttle, which is an important aspect of the reaction mechanism of alpha-class carbonic anhydrases. A hydrophobic pocket on the surface of the enzyme may participate in the trapping of CO(2) at the active site. On the basis of the coordination geometry at the active site, ligand binding modes, the behavior of the side chains of Glu 62 and Glu 84, and analogies to the well-characterized alpha-class of carbonic anhydrases, a more-defined reaction mechanism is proposed for the gamma-class of carbonic anhydrases.
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(as it appears on PubMed at http://www.pubmed.gov), where 10924115 is the PubMed ID number.
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{{ABSTRACT_PUBMED_10924115}}
==About this Structure==
==About this Structure==
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[[Category: Beta-helix]]
[[Category: Beta-helix]]
[[Category: Lyase]]
[[Category: Lyase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 06:37:37 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 19:34:22 2008''

Revision as of 16:34, 27 July 2008

Image:1qrm.png

Template:STRUCTURE 1qrm

A CLOSER LOOK AT THE ACTIVE SITE OF GAMMA-CARBONIC ANHYDRASES: HIGH RESOLUTION CRYSTAL STRUCTURES OF THE CARBONIC ANHYDRASE FROM METHANOSARCINA THERMOPHILA

Template:ABSTRACT PUBMED 10924115

About this Structure

1QRM is a Single protein structure of sequence from Methanosarcina thermophila. Full crystallographic information is available from OCA.

Reference

A closer look at the active site of gamma-class carbonic anhydrases: high-resolution crystallographic studies of the carbonic anhydrase from Methanosarcina thermophila., Iverson TM, Alber BE, Kisker C, Ferry JG, Rees DC, Biochemistry. 2000 Aug 8;39(31):9222-31. PMID:10924115

Page seeded by OCA on Sun Jul 27 19:34:22 2008

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