Ubiquinone analogue inhibitors and the structure of complex I

Wong, Jonathan (2017) Ubiquinone analogue inhibitors and the structure of complex I. MSc(R) thesis, University of Glasgow.

Abstract

Complex I (NADH-ubiquinone oxidoreductase) plays a central role in oxidative phosphorylation and ultimately ATP synthesis. It couples the energy released from the transfer of electrons from NADH to Q (through various redox cofactors contained within the enzyme itself) with proton translocation, by a mechanism that is still currently unknown. Complex I dysfunction is implicated in many severe clinical conditions in humans and other mammals; which are mostly neurodegenerative in nature. Complex I is also a major site of ROS production within the mitochondria, which can lead to oxidative damage involved in the aging process and pathological conditions such as ischemia-reperfusion injury.
Due to the large size and complexity of this multi-subunit enzyme, a full crystal structure of the minimal bacterial complex from T. thermophilus was published only recently in 2013. X-ray crystal structures from eukaryotic species such as Y. lipolytica were also later published. Structural data obtained by cryo-electron microscopy on the mammalian enzyme from B. taurus also followed soon after. These structural data together confirm the conservation of 14 core subunits (constituting a L shaped structure) that are sufficient for catalytic function and suggest a common catalytic mechanism. Though much structural data from both X-ray crystallography and cryo-EM is now available, the actual redox-coupled proton translocation mechanism still remains elusive. Structural data of the enzyme in different redox states or conformations caused by the binding of substrates may allow for such catalytic mechanism to be determined. Structural data for a bound decylubiquinone has been published, showing the binding site of the quinone head group. The location of the short alkyl chain led to the proposal of a putative channel through which Q is thought to enter and leave its binding site. However, structural data of the enzyme with a natural bound Q has not yet been observed, leaving much questions about the dynamics of Q binding and QH2 release and its role in the redox-coupled proton translocation mechanism.
In this project, various novel strong binding Q analogue inhibitors based on the structures of two known Q-site inhibitors were synthesized in the hope of obtaining structural data for these bound to complex I. This would be expected to provide further insight into the mechanism by which complex I functions. One of our Q analogue inhibitors has shown good binding affinity to the Q-site with an IC50 of 8.7nM. This and preliminary results from other analogues indicate that further information on the structure and dynamics of complex I will be obtained.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Keywords: Complex I, ubiquinone analogues, Q-site inhibitors, structure of complex I.
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Hartley, Professor Richard C.
• Date of Award: 2017
• Embargo Date: 2 February 2020
• Depositing User: Mr. Jonathan Wong
• Unique ID: glathesis:2017-7913
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 13 Feb 2017 13:01
• Last Modified: 07 Jun 2024 15:19
• URI: https://theses.gla.ac.uk/id/eprint/7913