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1sy7

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{{STRUCTURE_1sy7| PDB=1sy7 | SCENE= }}
{{STRUCTURE_1sy7| PDB=1sy7 | SCENE= }}
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'''Crystal structure of the catalase-1 from Neurospora crassa, native structure at 1.75A resolution.'''
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===Crystal structure of the catalase-1 from Neurospora crassa, native structure at 1.75A resolution.===
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==Overview==
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Catalase-1, one of four catalase activities of Neurospora crassa, is associated with non-growing cells and accumulates in asexual spores. It is a large, tetrameric, highly efficient, and durable enzyme that is active even at molar concentrations of hydrogen peroxide. Catalase-1 is oxidized at the heme by singlet oxygen without significant effects on enzyme activity. Here we present the crystal structure of catalase-1 at 1.75A resolution. Compared to structures of other catalases of the large class, the main differences were found at the carboxy-terminal domain. The heme group is rotated 180 degrees around the alpha-gamma-meso carbon axis with respect to clade 3 small catalases. There is no co-ordination bond of the ferric ion at the heme distal side in catalase-1. The catalase-1 structure exhibited partial oxidation of heme b to heme d. Singlet oxygen, produced catalytically or by photosensitization, may hydroxylate C5 and C6 of pyrrole ring III with a subsequent formation of a gamma-spirolactone in C6. The modification site in catalases depends on the way dioxygen exits the protein: mainly through the central channel or the main channel in large and small catalases, respectively. The catalase-1 structure revealed an unusual covalent bond between a cysteine sulphur atom and the essential tyrosine residue of the proximal side of the active site. A peptide with the predicted theoretical mass of the two bound tryptic peptides was detected by mass spectrometry. A mechanism for the Cys-Tyr covalent bond formation is proposed. The tyrosine bound to the cysteine residue would be less prone to donate electrons to compound I to form compound II, explaining catalase-1 resistance to substrate inhibition and inactivation. An apparent constriction of the main channel at Ser198 lead us to propose a gate that opens the narrow part of the channel when there is sufficient hydrogen peroxide in the small cavity before the gate. This mechanism would explain the increase in catalytic velocity as the hydrogen peroxide concentration rises.
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{{ABSTRACT_PUBMED_15342250}}
==About this Structure==
==About this Structure==
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[[Category: Neurospora crassa]]
[[Category: Neurospora crassa]]
[[Category: Singlet oxygen]]
[[Category: Singlet oxygen]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 09:16:23 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 05:47:53 2008''

Revision as of 02:47, 29 July 2008

Image:1sy7.png

Template:STRUCTURE 1sy7

Crystal structure of the catalase-1 from Neurospora crassa, native structure at 1.75A resolution.

Template:ABSTRACT PUBMED 15342250

About this Structure

1SY7 is a Single protein structure of sequence from Neurospora crassa. Full crystallographic information is available from OCA.

Reference

Unusual Cys-Tyr covalent bond in a large catalase., Diaz A, Horjales E, Rudino-Pinera E, Arreola R, Hansberg W, J Mol Biol. 2004 Sep 17;342(3):971-85. PMID:15342250

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