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Title: Critical Role of Water Molecules in Proton Translocation by the Membrane-Bound Transhydrogenase

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1374338
DOE Contract Number:
AC02-76SF00515; 5R01GM103838; R01HL16101; 1S10OD012289-01A1; TG-MCB150029; ACB-12002; AGM-12006; P41GM103393; AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Structure; Journal Volume: 25; Journal Issue: 7
Country of Publication:
United States
Language:
English

Citation Formats

Padayatti, Pius S., Leung, Josephine H., Mahinthichaichan, Paween, Tajkhorshid, Emad, Ishchenko, Andrii, Cherezov, Vadim, Soltis, S. Michael, Jackson, J. Baz, Stout, C. David, Gennis, Robert B., and Zhang, Qinghai. Critical Role of Water Molecules in Proton Translocation by the Membrane-Bound Transhydrogenase. United States: N. p., 2017. Web. doi:10.1016/j.str.2017.05.022.
Padayatti, Pius S., Leung, Josephine H., Mahinthichaichan, Paween, Tajkhorshid, Emad, Ishchenko, Andrii, Cherezov, Vadim, Soltis, S. Michael, Jackson, J. Baz, Stout, C. David, Gennis, Robert B., & Zhang, Qinghai. Critical Role of Water Molecules in Proton Translocation by the Membrane-Bound Transhydrogenase. United States. doi:10.1016/j.str.2017.05.022.
Padayatti, Pius S., Leung, Josephine H., Mahinthichaichan, Paween, Tajkhorshid, Emad, Ishchenko, Andrii, Cherezov, Vadim, Soltis, S. Michael, Jackson, J. Baz, Stout, C. David, Gennis, Robert B., and Zhang, Qinghai. Sat . "Critical Role of Water Molecules in Proton Translocation by the Membrane-Bound Transhydrogenase". United States. doi:10.1016/j.str.2017.05.022.
@article{osti_1374338,
title = {Critical Role of Water Molecules in Proton Translocation by the Membrane-Bound Transhydrogenase},
author = {Padayatti, Pius S. and Leung, Josephine H. and Mahinthichaichan, Paween and Tajkhorshid, Emad and Ishchenko, Andrii and Cherezov, Vadim and Soltis, S. Michael and Jackson, J. Baz and Stout, C. David and Gennis, Robert B. and Zhang, Qinghai},
abstractNote = {},
doi = {10.1016/j.str.2017.05.022},
journal = {Structure},
number = 7,
volume = 25,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}
  • N,N'-Dicyclohexylcarbodiimide (DCCD) inhibits the mitochondrial energy-linked nicotinamidenucleotide transhydrogenase (TH). Recent studies suggested that the inhibition site of DCCD is near the NAD(H) binding site, because NAD(H) and competitive inhibitors protected TH against inhibition by DCCD and, unlike the unmodified TH, the DCCD-modified TH did not bind to NAD- agarose. Others could not demonstrate protection by NADH, obtained data indicating DCCD inhibits proton translocation by TH much more than hydride ion transfer from NADPH to 3-acetylpyridine adenine dinucleotide (AcPyAD), and concluded that DCCD modifies an essential residue in the proton channel of TH. The present studies show that N-(ethoxycarbonyl)-2- ethoxy-1,2-dihydroquinoline (EEDQ)more » also inhibits TH. The inhibition is pseudo first order at several EEDQ concentrations, and the reaction order with respect to (EEDQ) is unity, suggesting that inhibition involves the interaction of one molecule of EEDQ with one active unit of TH. The EEDQ-modified TH reacts covalently with (/sup 3/H)aniline, suggesting that the residue modified by EEDQ is a carboxyl group. More significantly, it has been shown that the absorbance change of oxonol VI at 630 minus 603 nm is a reliable reporter of TH-induced membrane potential formation in submitochondrial particles and that TH-catalyzed hydride ion transfer from NADPH to AcPyAD and the membrane potential induced by this reaction are inhibited in parallel by either DCCD or EEDQ.« less
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  • The efficiencies of the reaction MH/sup +/ + D/sub 2/O ..-->.. MD/sup +/ + HDO or the analogous reaction in which deuteration is reversed have been measured for the cases, M. = formaldehyde, acetaldehyde, methanol, methyl formate, propionaldehyde, dimethyl ether, 1,4-dioxane, acetone, diethyl ether, di-n-propyl ether, and pyridine. A quantitative evaluation of the model used in estimating well depths leads to the conclusion that the energies of association in such complexes are primarily electrostatic in nature, since the model, which considers only electrostatic interactions, predicts well depths in close agreement with those obtained by experiment or ab initio calculations. Usemore » of this approximation also correctly predicts the experimentally determined well depths for the systems studied here and permits one to assign the structure (MH/sup +/ H/sub 2/O) to the most stable configurations of the proton-bound complexes in all cases except the formaldehyde-water system, where the complexes have the structure (H/sub 2/CO H/sub 3/O/sup +/); this is verified by the observation that the statistically corrected probability for isotope exchange in this system is unity. In the acetaldehyde-, methanol-, methyl formate-, propionaldehyde-, and dimethyl ether-water systems, the (M H/sub 3/O/sup +/) complexes are prediced to be energetically accessible to separated reactants and, in all these cases, isotope exchange is seen to occur, with a statistically corrected probability of 0.85 to 0.42, depending on the energetics of the proton transfer in the complex. For the 1,4-dioxane-, diethyl ether-, di-n-propyl ether-, and pyridine-water systems, where the model predicts that the (M H/sub 3/O/sup +/) complex is energetically inaccessible, isotope exchange is not observed. The implications of these results to the observed correlation between the heats of formation of association ions and the differences in proton affinities of the complexed molecules are discussed. 29 references.« less
  • Bovine heart cytochrome-c oxidase was reconstituted in liposomes and modified with N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). EEDQ reacted mainly with subunits II and III and to a lower extent with subunit I, as shown by difference labeling with ({sup 14}C)dicyclohexylcarbodiimide. EEDQ treatment of cytochrome-c oxidase vesicles influenced ferrocytochrome c-induced proton pumping by reducing maximally the H+/e- stoichiometry from 0.84 (control) to 0.24, but had only small effects on respiration, respiratory control ratio, and proton conductivity of the proteoliposomes. By titrating the reaction rate of the control and the modified cytochrome-c oxidase vesicles versus the membrane potential, as measured with a Ph3MeP+ electrode, saturationmore » curves are obtained, which in both cases approach 225 mV. The ratios of electron transport rates of the two proton pumps at various membrane potentials decrease between 160 and 225 mV from about 2.2 to 1, indicating that the nonlinear flow/force relationship of these proton pumps is at least partly due to 'slippage' of proton pumping.« less