Unexpected Roles of a Tether Harboring a Tyrosine Gatekeeper Residue in Modular Nitrite Reductase Catalysis



Hedison, TM, Shenoy, RT, Iorgu, AI, Heyes, DJ, Fisher, K, Wright, GSA ORCID: 0000-0002-3756-9634, Hay, S, Eady, RR, Antonyuk, Svetlana ORCID: 0000-0002-2779-9946, Hasnain, SS
et al (show 1 more authors) (2019) Unexpected Roles of a Tether Harboring a Tyrosine Gatekeeper Residue in Modular Nitrite Reductase Catalysis. ACS Catalysis, 9 (7). 6087 - 6099.

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Abstract

© 2019 American Chemical Society. It is generally assumed that tethering enhances rates of electron harvesting and delivery to active sites in multidomain enzymes by proximity and sampling mechanisms. Here, we explore this idea in a tethered 3-domain, trimeric copper-containing nitrite reductase. By reverse engineering, we find that tethering does not enhance the rate of electron delivery from its pendant cytochrome c to the catalytic copper-containing core. Using a linker that harbors a gatekeeper tyrosine in a nitrite access channel, the tethered haem domain enables catalysis by other mechanisms. Tethering communicates the redox state of the haem to the distant T2Cu center that helps initiate substrate binding for catalysis. It also tunes copper reduction potentials, suppresses reductive enzyme inactivation, enhances enzyme affinity for substrate, and promotes intercopper electron transfer. Tethering has multiple unanticipated beneficial roles, the combination of which fine-tunes function beyond simplistic mechanisms expected from proximity and restrictive sampling models.

Item Type: Article
Uncontrolled Keywords: copper nitrite reductase, tethering, enzyme catalysis, electron transfer, modular enzyme architecture, interprotein electron transfer, protein dynamics
Depositing User: Symplectic Admin
Date Deposited: 08 Jul 2019 08:11
Last Modified: 27 May 2020 10:09
DOI: 10.1021/acscatal.9b01266
Related URLs:
URI: http://livrepository.liverpool.ac.uk/id/eprint/3048917