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Title: Structural studies of the hydrophilic domain of complex I from Thermus thermophilus
Author: Hinchliffe, P.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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Complex I is the first enzyme in the respiratory chains of both mitochondria and bacteria and catalyses the transfer of two electrons from NADH to quinine. This is coupled to the translocation of approximately 4 protons across the membrane, contributing to the proton motive force, used to synthesise ATP. Mutations in complex I are implicated in many human neurodegenerative diseases. The mitochondrial enzyme consists of 45 different subunits, while the bacterial enzyme consists of 13-15 different subunits and retains many of the same properties. The bacterial enzyme is considered a good minimal model for studying complex I. The hydrophilic domain of complex I protrudes into the mitochondrial matrix (or bacterial cytoplasm) and contains all the known cofactors of the enzyme. A procedure for purifying the hydrophilic domain of complex I from T. thermophilus has been developed, allowing extensive studies on the enzyme to take place. The complex is extremely stable in many detergents and at a high temperature. EPR spectroscopic analysis identified the presence of at least 4 iron-sulphur clusters. In total, 8 subunits could be positively identified, including a previously unknown subunit of complex I, named Nqo15. It indicated the possibility complex I from other species may contain more subunits than originally thought. The first reported 3-D protein crystals of complex I (or of its subcomplexes), suitable for X-ray data collection, could be grown from the preparation. From these, the hydrophilic domain from T. thermophilus has been solved to 3.3 Å resolution. Additionally, from protein crystals grown in the presence of NADH, the binding site for this complex I substrate could also be elucidated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available