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- W1511424221 endingPage "208" @default.
- W1511424221 startingPage "79" @default.
- W1511424221 abstract "The plethora of proposed chemical models attempting to explain the proton pumping reactions catalyzed by the CcO complex, especially the number of recent models, makes it clear that the problem is far from solved. Although we have not discussed all of the models proposed to date, we have described some of the more detailed models in order to illustrate the theoretical concepts introduced at the beginning of this section on proton pumping as well as to illustrate the rich possibilities available for effecting proton pumping. It is clear that proton pumping is effected by conformational changes induced by oxidation/reduction of the various redox centers in the CcO complex. It is for this reason that the CcO complex is called a redox-linked proton pump. The conformational changes of the proton pump cycle are usually envisioned to be some sort of ligand-exchange reaction arising from unstable geometries upon oxidation/reduction of the various redox centers. However, simple geometrical rearrangements, as in the Babcock and Mitchell models are also possible. In any model, however, hydrogen bonds must be broken and reformed due to conformational changes that result from oxidation/reduction of the linkage site during enzyme turnover. Perhaps the most important point emphasized in this discussion, however, is the fact that proton pumping is a directed process and it is electron and proton gating mechanisms that drive the proton pump cycle in the forward direction. Since many of the models discussed above lack effective electron and/or proton gating, it is clear that the major difficulty in developing a viable chemical model is not formulating a cyclic set of protein conformational changes effecting proton pumping (redox linkage) but rather constructing the model with a set of physical constraints so that the proposed cycle proceeds efficiently as postulated. In our discussion of these models, we have not been too concerned about which electron of the catalytic cycle was entering the site of linkage, but merely whether an ET to the binuclear center played a role. However, redox linkage only occurs if ET to the activated binuclear center is coupled to the proton pump. Since all of the models of proton pumping presented here, with the exception of the Rousseau expanded model and the Wikström model, have a maximum stoichiometry of 1 H+/e-, they inadequately explain the 2 H+/e- ratio for the third and fourth electrons of the dioxygen reduction cycle (see Section V.B). One way of interpreting this shortfall of protons is that the remaining protons are pumped by an as yet undefined indirectly coupled mechanism. In this scenario, the site of linkage could be coupled to the pumping of one proton in a direct fashion and one proton in an indirect fashion for a given electron. For a long time, it was assumed that at least some elements of such an indirect mechanism reside in subunit III. While recent evidence argues against the involvement of subunit III in the proton pump, subunit III may still participate in a regulatory and/or structural capacity (Section II.E). Attention has now focused on subunits I and II in the search for residues intimately involved in the proton pump mechanism and/or as part of a proton channel. In particular, the role of some of the highly conserved residues of helix VIII of subunit I are currently being studied by site directed mutagenesis. In our opinion, any model that invokes heme alpha 3 or CuB as the site of linkage must propose a very effective means by which the presumedly fast uncoupling ET to the dioxygen intermediates is prevented. It is difficult to imagine that ET over the short distance from heme alpha 3 or CuB to the dioxygen intermediate requires more than 1 ns. In addition, we expect the conformational changes of the proton pump to require much more than 1 ns (see Section V.B)." @default.
- W1511424221 created "2016-06-24" @default.
- W1511424221 creator A5017196184 @default.
- W1511424221 creator A5017230178 @default.
- W1511424221 creator A5085962625 @default.
- W1511424221 date "1995-01-01" @default.
- W1511424221 modified "2023-09-23" @default.
- W1511424221 title "CytochromecOxidase: Chemistry of a Molecular Machine" @default.
- W1511424221 cites W104601146 @default.
- W1511424221 cites W1246794412 @default.
- W1511424221 cites W13095824 @default.
- W1511424221 cites W136081623 @default.
- W1511424221 cites W13931849 @default.
- W1511424221 cites W1459222285 @default.
- W1511424221 cites W1469975568 @default.
- W1511424221 cites W1478988028 @default.
- W1511424221 cites W1482203906 @default.
- W1511424221 cites W1489666943 @default.
- W1511424221 cites W1492833585 @default.
- W1511424221 cites W1493180615 @default.
- W1511424221 cites W1495656425 @default.
- W1511424221 cites W1498185925 @default.
- W1511424221 cites W1503744079 @default.
- W1511424221 cites W1504398414 @default.
- W1511424221 cites W1508115748 @default.
- W1511424221 cites W1508494737 @default.
- W1511424221 cites W1508734769 @default.
- W1511424221 cites W1511407237 @default.
- W1511424221 cites W1514336087 @default.
- W1511424221 cites W1514736137 @default.
- W1511424221 cites W1516667549 @default.
- W1511424221 cites W1520930022 @default.
- W1511424221 cites W1523705478 @default.
- W1511424221 cites W1524183389 @default.
- W1511424221 cites W1525331343 @default.
- W1511424221 cites W1527397773 @default.
- W1511424221 cites W1529254718 @default.
- W1511424221 cites W1533629889 @default.
- W1511424221 cites W1534977390 @default.
- W1511424221 cites W1538092103 @default.
- W1511424221 cites W1538319771 @default.
- W1511424221 cites W1540436913 @default.
- W1511424221 cites W1541197218 @default.
- W1511424221 cites W1541371426 @default.
- W1511424221 cites W1541840089 @default.
- W1511424221 cites W1543790289 @default.
- W1511424221 cites W1544518693 @default.
- W1511424221 cites W1545800501 @default.
- W1511424221 cites W1547052620 @default.
- W1511424221 cites W1550727253 @default.
- W1511424221 cites W1555467483 @default.
- W1511424221 cites W1556605629 @default.
- W1511424221 cites W1559682060 @default.
- W1511424221 cites W1561941585 @default.
- W1511424221 cites W1561990074 @default.
- W1511424221 cites W1562731883 @default.
- W1511424221 cites W1562871643 @default.
- W1511424221 cites W1563472611 @default.
- W1511424221 cites W1563739734 @default.
- W1511424221 cites W1564066839 @default.
- W1511424221 cites W1564321618 @default.
- W1511424221 cites W1564672781 @default.
- W1511424221 cites W1568687764 @default.
- W1511424221 cites W1570741201 @default.
- W1511424221 cites W1571405123 @default.
- W1511424221 cites W1571959349 @default.
- W1511424221 cites W1574150437 @default.
- W1511424221 cites W1576822037 @default.
- W1511424221 cites W1581619899 @default.
- W1511424221 cites W1581699805 @default.
- W1511424221 cites W1583540770 @default.
- W1511424221 cites W1585551835 @default.
- W1511424221 cites W1587079358 @default.
- W1511424221 cites W1588620084 @default.
- W1511424221 cites W1590226237 @default.
- W1511424221 cites W1590816720 @default.
- W1511424221 cites W1591741891 @default.
- W1511424221 cites W1595577364 @default.
- W1511424221 cites W1597506391 @default.
- W1511424221 cites W1597560852 @default.
- W1511424221 cites W1597844740 @default.
- W1511424221 cites W1607298047 @default.
- W1511424221 cites W1607449281 @default.
- W1511424221 cites W160896424 @default.
- W1511424221 cites W1637969949 @default.
- W1511424221 cites W1650134562 @default.
- W1511424221 cites W1676079444 @default.
- W1511424221 cites W1680438645 @default.
- W1511424221 cites W1725455808 @default.
- W1511424221 cites W174034613 @default.
- W1511424221 cites W1749436095 @default.
- W1511424221 cites W1761464280 @default.
- W1511424221 cites W1769845314 @default.
- W1511424221 cites W1771270360 @default.
- W1511424221 cites W1791689008 @default.
- W1511424221 cites W1886180589 @default.
- W1511424221 cites W1923391594 @default.
- W1511424221 cites W1963567649 @default.