Adenosine triphosphate (ATP) is the molecular currency of intracellular energy transfer in living organisms. The enzyme ATP synthase is primarily responsible for ATP production in eukaryotes. In archaea and some bacteria, ATP is synthesized by V-ATPase that is related to ATP synthase both in structure and function. Both of these enzymes are reversible rotary motors
capable of catalyzing ATP synthesis or hydrolysis. The rotation of the central rotor, which is powered by the flow of proton (or sometimes sodium ion) down the electrochemical gradient through the membrane-bound Fo/Vo region, leads to the chemical synthesis of ATP in F1/V1 region. The F1/V1 region, on the other hand, can catalyze ATP hydrolysis, which in turn leads to proton (or sodium) pumping across the membrane through rotation of the central rotor in the opposite direction. This thesis describes structure determination of both the intact F-type and V-type enzymes using single particle electron cryomicroscopy (cryo-EM), with the aim of better
understanding their overall architecture, subunit organization and the mechanism of proton translocation.
Our cryo-EM structural analysis on the F-type ATP synthase from Saccharomyces
cerevisiae uncovered the arrangement of subunits a, b, c, and the two dimer-specific subunits e and g within the membrane-bound region of Fo. A model of oligomerization of the ATP synthase involving two distinct dimerization interfaces was proposed.The rotor-stator interaction within the membrane-bound region of both enzymes is
responsible for proton translocation. Our cryo-EM structures of the V-ATPase from Thermus thermophilus reveal that the interaction between the rotary ring (rotor) and the I-subunit (stator) is surprisingly small, with only two subunits from the ring making contact with the I-subunit near the middle of the membrane. Furthermore, the spatial arrangement of transmembrane helices
resolved in subunit I can form two passageways that could provide proton access through the membrane-bound region and is consistent with a two-channel model of proton translocation.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/32804 |
| Date | 31 August 2012 |
| Creators | Lau, Wilson |
| Contributors | Rubinstein, John |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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