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Does Tyrosine Protect S. Coelicolor Laccase from Oxidative Degradation?

Kielb, Patrycja J. and Gray, Harry B. and Winkler, Jay R. (2020) Does Tyrosine Protect S. Coelicolor Laccase from Oxidative Degradation? . (Unpublished)

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We have investigated the roles of tyrosine (Tyr) and tryptophan (Trp) residues in the four-electron reduction of oxygen catalyzed by Streptomyces coelicolor laccase (SLAC). During normal enzymatic turnover in laccases, reducing equivalents are delivered to a type 1 Cu center (Cu_(T1)) and then are transferred over 13 Å to a trinuclear Cu site (TNC: (Cu_(T3))₂Cu_(T2)) where O₂ reduction occurs. The TNC in SLAC is surrounded by a large cluster of Tyr and Trp residues that can provide reducing equivalents when the normal flow of electrons is disrupted. Canters and coworkers have shown that when O₂ reacts with a reduced SLAC variant lacking the CuT1 center, a Tyr108· radical near the TNC forms rapidly. We have found that ascorbate reduces the Tyr108· radical in wild-type SLAC about 10 times faster than it reacts with the Cu_(T1)²⁺ center, possibly owing to radical transfer along a Tyr/Trp chain. Aerobic oxidation of two reduced SLAC mutants (Y108F and W132F) leads to the formation of a long-lived (~15 min) Tyr· radical with distinct absorption at 408 nm. The diffusion of redox equivalents away from the primary enzymatic pathway in SLAC may indicate a poorly optimized enzyme or a mechanism to protect against protein damage.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Kielb, Patrycja J.0000-0003-2809-0813
Gray, Harry B.0000-0002-7937-7876
Winkler, Jay R.0000-0002-4453-9716
Additional Information:Licence: CC BY-NC-ND 4.0. Submitted date: 18/07/2020; Posted date: 20/07/2020. Funding: National Institute of Diabetes and Digestive and Kidney Diseases. Authors declare no conflict of interest.
Funding AgencyGrant Number
National Institute of Diabetes and Digestive and Kidney DiseasesUNSPECIFIED
Subject Keywords:electron transfer; oxygen reduction; enzyme kinetics; tyrosyl radical; small laccase
Record Number:CaltechAUTHORS:20200720-145555975
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104465
Deposited By: Tony Diaz
Deposited On:21 Jul 2020 15:41
Last Modified:16 Nov 2021 18:32

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