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Title
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On the track of long-range electron transfer in B-type dye-decolorizing peroxidases : identification of a tyrosyl radical by computational prediction and electron paramagnetic resonance spectroscopy
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Author
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Abstract
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| The catalytic activity of dye-decolorizing peroxidases (DyPs) toward bulky substrates, including anthraquinone dyes, phenolic lignin model compounds, or 2,2'-azino-bis(3-ethylbenzothia-zoline-6-sulfonic acid) (ABTS), is in strong contrast to their sterically restrictive active site. In two of the three known subfamilies (A- and C/D-type DyPs), catalytic protein radicals at surface-exposed sites, which are connected to the heme cofactor by electron transfer path(s), have been identified. So far in B-type DyPs, there has been no evidence for protein radical formation after activation by hydrogen peroxide. Interestingly, B-type Klebsiella pneumoniae dye-decolorizing peroxidase (KpDyP) displays a persistent organic radical in the resting state composed of two species that can be distinguished by W-band electron spin echo electron paramagnetic resonance (EPR) spectroscopy. Here, on the basis of a comprehensive mutational and EPR study of computationally predicted tyrosine and tryptophan variants of KpDyP, we demonstrate the formation of tyrosyl radicals (Y247 and Y92) and a radical-stabilizing Y-W dyad between Y247 and W18 in KpDyP, which are unique to enterobacterial B-type DyPs. Y247 is connected to Y92 by a hydrogen bonding network, is solvent accessible in simulations, and is involved in ABTS oxidation. This suggests the existence of long-range electron path(s) in B-type DyPs. The mechanistic and physiological relevance of the reaction mechanism of B-type DyPs is discussed. |
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Language
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English
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Source (journal)
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Biochemistry / American Chemical Society. - Washington, D.C., 1962, currens
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Publication
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Washington, D.C.
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2021
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ISSN
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0006-2960
[print]
1520-4995
[online]
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DOI
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10.1021/ACS.BIOCHEM.1C00129
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Volume/pages
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60
:15
(2021)
, p. 1226-1241
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ISI
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000643538900008
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Pubmed ID
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33784066
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Full text (Publisher's DOI)
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Full text (open access)
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