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The State of the Science Human Studies
It is known that oligomycin inhibits swelling and shrinkage as well as the activity of ATPase (Lehninger ), and oligomycin sensitivity-conferring protein is necessary for perfect binding of F1-subunit with F0-subunit (Racker ). Also, electron microscopy data show that low-amplitude changes of mitochondria volumes occur between matrix and intermembrane space (Hackenbrock ; Lehninger ; Harris et al. ). Then, we may conclude that swelling–shrinkage of intermembrane space as well as thylakoids in chloroplasts occurs through ATP synthase.
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Lohrasebi and Feshanjerdi () have stated that F0 is the ion pump as opposed to the dominant opinion that the c-ring is the rotor; they have even built a pump, which is capable of producing a gradient of ions. It has a blade, which pumps ions from one compartment to another. Operation of this pump is similar to the principle of c-ring as ion channel. Many experimental facts agree with the mechanism presented by our model; some of these are listed below:
Which of the following statements is not true of most cellular ..
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We believe that in the presence of oxidative substrate, phosphate ions, ADP, and other essential ions for the formation of ATP, in energization of mitochondria, we will observe the following processes in the sequence:
We are aware that the view presented here is not accepted by other model, but is presented here for further examination and testing, so that we may reach a final conclusion on this important problem. In order to prove the mechano-chemiosmotic model of coupling, it is necessary to perform further kinetic experiments (it is desirable to simultaneously obtain different parameters) on individual organelles in millisecond time scale:
Physiological Chemistry and Physics and Medical NMR
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Later, this chemiosmotic hypothesis was refined in terms of proton transfer (Mitchell ), and the idea was proposed that the hydrophobic component of ATPase-F0 is oligomycin sensitive proton channel through the membrane. Thus, F1 is attached to F0 so that its active center faces the proton channel F0. As a result of ATP hydrolysis, the protons are released into the channel, while ADP and Pi are transported back through F1 to the aqueous phase. However, in the synthesis of ATP, protons are picked up from the proton channel by phosphate, and phosphorylation of ADP occurs in the active center of F1.
Boyer () presented another hypothesis for ATP synthesis; it was a conformational change hypothesis, which assumed that energy storage takes place by conformational changes in proteins of the electron transport chain, involving “contraction and relaxation” of the enzyme, similar to the well-known actin–myosin system. In some ways, this conformational hypothesis is reminiscent of the chemical hypothesis; it had its adherents (Lehninger ; Harris et al. ), who were attracted by the existence of mitochondrial conformational changes during oxidative phosphorylation. According to one view of the conformational hypothesis, ATP, per se, does not have energy to give, and energy is not needed for ATP synthesis in vivo (Banks and Vernon ). In agreement with this version of conformational hypothesis, Paul Boyer later suggested that energy is not required for ATP synthesis, and energy of protein conformational changes, coupled with the membrane potential and protonation–deprotonation, is actually used for the release of ATP from ATPase/ATP synthase (Boyer ).
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Plant Energy Transformations-Photosynthesis - …
To investigate the sequential stepping of the proton-driven c-ring rotation, Duser et al. () fused enhanced green fluorescent protein (EGFP) as fluorescence resonance energy transfer (FRET) donor to the C-terminus of the a-subunit. Alexa568-maleimide was used as a FRET acceptor and was covalently bound to a cysteine (E2C mutation) of one c-subunit. ATP synthase molecules were reconstituted singly into liposomes, which then had ATP synthesis activity. The radius of the FRET acceptor rotation was 2.5 nm on the c-ring. We suggest that the authors interpreted incorrectly a correct experiment that was performed in a membrane. Since, the FRET acceptor was covalently bound only to a cysteine (E2C mutation) of one c-subunit, then a FRET acceptor will bind at the first ATP synthase to the first c-monomer beginning from the a-subunit in a clockwise direction; at the second ATP synthase, it will bind to the second c-monomer, and at the third ATP synthase it will bind to the third c-monomer. At the same time, it is known that conformational changes of the subunit c occur during the protonation–deprotonation of Asp 61(Rastogi and Girvin ), and the structure of c-ring is deformed during energization of the membrane. In this case, the FRET signals will arrive at an average from all c-monomers of all ATP synthases as the integral signal, and a deformation of the structure of c-ring during energization was interpreted by the authors (Duser et al. ) as the c-ring rotation.
NEET 2018 Preparation Study Material , TopperLearning
Thus, we suggest that all researchers must take into account, in their studies, for manipulation with the rotation of ATP synthase subunits, an absolute dependence of results on the place of attachment of the subunits. This conclusion is supported by experiments of Tanabe et al. (), where the γεc10–14-complex is a mechanical unit of the enzyme, and, it can be used as a rotor or a stator experimentally, depending on which subunit is immobilized. The membrane parts of F0c-subunits must be integrated exclusively in the membrane where they attach themselves naturally. Under these conditions, the c-subunit of the F0 part of ATP synthase has the ability for free conformational changes, where a conformational change of the c-ring might transform it to a non-selective pore (Chinopoulos and Szabadkai ). The c-subunit of the mitochondrial F1-F0ATP synthase, which is located on the all surfaces of inner membrane, has been recently found to be a fundamental component of the mitochondrial permeability transition pore—mPTP (Bonora et al. ; Alavian et al. ). The mPTP is a high-conductance channel that is located at the contact sites between the inner and outer mitochondrial membranes. The molecular composition of the mPTP is not yet clear, but several proteins have been shown to be its component that participate in mPTP activity, including voltage-dependent anion channels (VDAC), adenine nucleotide translocase (ANT), and the inorganic phosphate carrier (PiC) (De Marchi et al. , and references therein). Ca2+ ions, prooxidant, and proapoptotic proteins, a decrease in the mitochondrial membrane potential, pH variations, and adenine nucleotides all sensitize the opening of the pore (Baumgartner et al. ). The mPTP channel is responsible for the non-selective permeability state of the mitochondrial inner membrane. De Marchi et al. () observed that forcing mPTP opening or closing did not impair mitochondrial Ca2+ efflux. Therefore, in the opinion of the authors, their results strongly suggest that the mPTP does not participate in mitochondrial Ca2+ homeostasis in a physiological context in HeLa cells (De Marchi et al. ).
Bioelectromagnetic Healing - Integrity Research Institute
Tsunoda et al. () noted that the rotation of the c-subunit is probably due to release of the c-subunit ring from its critical interaction with the a-subunit. Further, according Sambongi et al. (), rotation of the c-ring was lost rapidly. This can be explained if the c-subunit ring, once displaced from the a-subunit, is only weakly bound to the γ-subunits and is quickly released by the viscous drag due to the torque of the rotation (Tsunoda et al. ). It was shown that “the c subunit rotation could be observed in the presence of Triton X-100 but not in the absence of the detergent” (Sambongi et al. ; Tsunoda et al. ).
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