Identifying the mechanism of second proton release from the bc1 complex Qo-site

The cytochrome bc1 complex and its family members play a central role in biological energy transduction across all domains of life, oxidizing QH2 in a bifurcated reaction which generates a proton-motive force used for ATP synthesis. It is widely accepted to operate according to a modified Q-cycle, but there is still debate over some aspects of the mechanism. We used the pH-sensitive dye neutral red to study the release of protons from the bc1 complex, with specific focus of the mechanism for release of the second proton from the Qo-site. Partial processes for the proton release could be isolated through use of different inhibitors, and correlated with electron transfers through the complex. We tested mutations at residues R94, N279, and Y147 in the b subunit of the complex, which are thought to interact with the water chain which provides a pathway for release of the second proton. Mutants R94A, N279F, and Y147T showed a significant decrease in proton release for a second turnover compared to the first, an indicator that the proton from the first turnover had difficulty leaving the complex. The latter two mutants also showed an intriguing difference in kinetics for the proton release and electron transfers for the first turnover.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biophysics & Computnl Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2017

Author dc:creator

• Wilson, Charles Alexander

Contributors dc:contributor

• Crofts, Antony
• Aksimentiev, Oleksii
• Gennis, Robert
• Gruebele, Martin

• Bc1 complex
• Rhodobacter sphaeroides

Statement dc:rights

• Copyright 2017 Charles Wilson

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/97425

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/97425