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Unexpected roles of a tether harboring a tyrosine gatekeeper residue in modular nitrite reductase catalysis

DOI: 10.1021/acscatal.9b01266 DOI Help

Authors: Tobias Hedison (The University of Manchester) , Rajesh Shenoy (University of Liverpool) , Andreea Iulia Iorgu (The University of Manchester) , Derren Heyes (The University of Manchester) , Karl Fisher (The University of Manchester) , Gareth Wright (University of Liverpool) , Sam Hay (The University of Manchester) , Robert Roy Eady (University of Liverpool) , Svetlana Antonyuk (University of Liverpool) , S. Samar Hasnain (University of Liverpool) , Nigel S. Scrutton (The University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Catalysis

State: Published (Approved)
Published: May 2019
Diamond Proposal Number(s): 11740

Abstract: It is generally assumed that tethering enhances rates of electron harvesting and delivery to active sites in multi-domain 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 inter-copper 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.

Journal Keywords: Copper nitrite reductase; tethering; enzyme catalysis; electron transfer; modular enzyme architecture; intraprotein electron transfer; interprotein electron transfer; protein dynamics

Subject Areas: Chemistry


Instruments: I03-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength) , I24-Microfocus Macromolecular Crystallography

Other Facilities: SOLEIL