2IH9: A High-dose Crystal Structure Of A Recombinant Melanocarbus Albomyces Laccase

Citation:
Abstract
Laccases (p-diphenol dioxygen oxidoreductases) belong to the family of blue multicopper oxidases, which catalyse the four-electron reduction of dioxygen to water concomitantly through the oxidation of substrate molecules. Blue multicopper oxidases have four coppers, a copper (T1) forming a mononuclear site and a cluster of three coppers (T2, T3, and T3') forming a trinuclear site. Because X-rays are known to liberate electrons during data collection and may thus affect the oxidation state of metals, we have investigated the effect of X-ray radiation upon the crystal structure of a recombinant laccase from Melanocarpus albomyces through the use of crystallography and crystal absorption spectroscopy. Two data sets with different strategies, a low and a high-dose data set, were collected at synchrotron. We have observed earlier that the trinuclear site had an elongated electron density amidst coppers, suggesting dioxygen binding. The low-dose synchrotron structure showed similar elongated electron density, but the high-dose X-ray radiation removed the bulk of this density. Therefore, X-ray radiation could alter the active site of laccase from M. albomyces. Absorption spectra of the crystals (320, 420, and 590nm) during X-ray radiation were measured at a home laboratory. Spectra clearly showed how that the band at 590nm had vanished, resulting from the T1 copper being reduced, during the long X-ray measurements. The crystal colour changed from blue to colourless. Absorptions at 320 and 420nm seemed to be rather permanent. The absorption at 320nm is due to the T3 coppers and it is proposed that absorption at 420nm is due to the T2 copper when dioxygen or a reaction intermediate is close to this copper.
PDB ID: 2IH9Download
MMDB ID: 42949
PDB Deposition Date: 2006/9/26
Updated in MMDB: 2012/12
Experimental Method:
x-ray diffraction
Resolution: 2  Å
Source Organism:
Similar Structures:
Biological Unit for 2IH9: monomeric; determined by author
Molecular Components in 2IH9
Label Count Molecule
Protein (1 molecule)
1
Laccase-1
Molecule annotation
Chemicals (19 molecules)
1
11
2
1
3
4
4
1
5
2
* Click molecule labels to explore molecular sequence information.

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