Kinetics of CO binding to putative Na+‐motive oxidases of the o‐type from Bacillus FTU and of the d‐type from Escherichia coli

Muntyan, Maria S.; Bloch, Dmitry A.; Drachev, Lel A.; Скулачев, В.П.

doi:10.1016/0014-5793(93)81018-u

Cited by 15 publications

(10 citation statements)

References 18 publications

(9 reference statements)

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“…Therefore, this spectrum can be undoubtedly assigned to CO binding to heme d in the R cytochrome bd . The characteristic time of this phase (τ∼20 µs at 1 mM CO) corresponds to a second-order rate constant of CO recombination to heme d of ∼ 5×10 7 M −1 ·s −1 , in agreement with the previously reported values for cytochrome bd from E. coli [60], [61] and A. vinelandii [42], [62]. As shown earlier [41], [43], [46], unlike the MV state, the R state reveals no geminate but only bimolecular recombination after photodissociation of CO from heme d .…”

Section: Resultssupporting

confidence: 91%

Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

et al. 2014

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Cytochrome bd is a tri-heme (b 558, b 595, d) respiratory oxygen reductase that is found in many bacteria including pathogenic species. It couples the electron transfer from quinol to O2 with generation of an electrochemical proton gradient. We examined photolysis and subsequent recombination of CO with isolated cytochrome bd from Escherichia coli in one-electron reduced (MV) and fully reduced (R) states by microsecond time-resolved absorption spectroscopy at 532-nm excitation. Both Soret and visible band regions were examined. CO photodissociation from MV enzyme possibly causes fast (τ<1.5 µs) electron transfer from heme d to heme b 595 in a small fraction of the protein, not reported earlier. Then the electron migrates to heme b 558 (τ∼16 µs). It returns from the b-hemes to heme d with τ∼180 µs. Unlike cytochrome bd in the R state, in MV enzyme the apparent contribution of absorbance changes associated with CO dissociation from heme d is small, if any. Photodissociation of CO from heme d in MV enzyme is suggested to be accompanied by the binding of an internal ligand (L) at the opposite side of the heme. CO recombines with heme d (τ∼16 µs) yielding a transient hexacoordinate state (CO-Fe2+-L). Then the ligand slowly (τ∼30 ms) dissociates from heme d. Recombination of CO with a reduced heme b in a fraction of the MV sample may also contribute to the 30-ms phase. In R enzyme, CO recombines to heme d (τ∼20 µs), some heme b 558 (τ∼0.2–3 ms), and finally migrates from heme d to heme b 595 (τ∼24 ms) in ∼5% of the enzyme population. Data are consistent with the recent nanosecond study of Rappaport et al. conducted on the membranes at 640-nm excitation but limited to the Soret band. The additional phases were revealed due to differences in excitation and other experimental conditions.

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Section: Resultssupporting

confidence: 91%

Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

et al. 2014

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“…Earlier, recombination of CO with the dithionite-reduced E. coli membranes containing the WT cytochrome bd was studied on the micro/millisecond time scale at the 532 nm excitation [57]. These membranes were treated with detergent.…”

Section: Discussionmentioning

confidence: 99%

“…However, treatment of cytochrome bd with detergent can lead to appearance of a denatured fraction of heme b reacting with CO [2, 56]. Such a heme b -CO complex can be easily photolyzed at the 532 nm excitation that resulted in additional slower phases of CO recombination with heme b [40, 54, 57], significantly complicating interpretation of the data [57]. In the present experiments, native membranes of E. coli , devoid of such an undesired reaction, were used.…”

Section: Discussionmentioning

confidence: 99%

Heme–heme and heme–ligand interactions in the di-heme oxygen-reducing site of cytochrome bd from Escherichia coli revealed by nanosecond absorption spectroscopy

Rappaport

Zhang

Vos

et al. 2010

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Summary Cytochrome bd is a terminal quinol:O2 oxidoreductase of respiratory chains of many bacteria. It contains three hemes, b558, b595, and d. The role of heme b595 remains obscure. A CO photolysis/recombination study of the membranes of Escherichia coli containing either wild type cytochrome bd or inactive E445A mutant was performed using nanosecond absorption spectroscopy. We compared photoinduced changes of heme d-CO complex in one-electron-reduced, two-electron-reduced, and fully-reduced states of cytochromes bd. The line shape of spectra of photodissociation of one-electron-reduced and two-electron-reduced enzymes is strikingly different from that of the fully-reduced enzyme. The difference demonstrates that in the fully-reduced enzyme photolysis of CO from heme d perturbs ferrous heme b595 causing loss of an absorption band centered at 435 nm, thus supporting interactions between heme b595 and heme d in the di-heme oxygen-reducing site, in agreement with previous works. Photolyzed CO recombines with the fully-reduced enzyme monoexponentially with τ ~12 µs, whereas recombination of CO with one-electron-reduced cytochrome bd shows three kinetic phases, with τ ~14 ns, 14 µs, and 280 µs. The spectra of the absorption changes associated with these components are different in line shape. The 14 ns phase, absent in the fully-reduced enzyme, reflects geminate recombination of CO with part of heme d. The 14 µs component reflects bimolecular recombination of CO with heme d and electron backflow from heme d to hemes b in ~4% of the enzyme population. The final, 280 µs component, reflects return of the electron from hemes b to heme d and bimolecular recombination of CO in that population. The fact that even in the two-electron-reduced enzyme, a nanosecond geminate recombination is observed, suggests that namely the redox state of heme b595, and not that of heme b558, controls the pathway(s) by which CO migrates between heme d and the medium.

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“…The apparent K d for the CO-heme d complex with the fully reduced ( R 3 ) cytochrome bd -I from E. coli was determined to be ~80 nM [255]. The R 3 cytochrome bd can form a photosensitive heme d -CO complex [258]. Flash photolysis of CO bound to heme d at cryogenic temperatures results in a redistribution of CO such that as much 15% of heme b 595 is bound to CO, showing the proximity of these two hemes [35].…”

Section: Binding Of Ligands (Other Than O2)mentioning

confidence: 99%

The cytochrome bd respiratory oxygen reductases

Borisov

Gennis

Hemp

et al. 2011

Biochimica et Biophysica Acta (BBA) - Bioenergetics

448

552

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Summary Cytochrome bd is a respiratory quinol:O2 oxidoreductase found in many prokaryotes, including a number of pathogens. The main bioenergetic function of the enzyme is the production of a proton motive force by the vectorial charge transfer of protons. The sequences of cytochromes bd are not homologous to those of the other respiratory oxygen reductases, i.e., the heme-copper oxygen reductases or alternative oxidases (AOX). Generally, cytochromes bd are noteworthy for their high affinity for O2 and resistance to inhibition by cyanide. In E. coli, for example, cytochrome bd (specifically, cytochrome bd-I) is expressed under O2-limited conditions. Among the members of the bd-family are the so-called cyanide-insensitive quinol oxidases (CIO) which often have a low content of the eponymous heme d but, instead, have heme b in place of heme d in at least a majority of the enzyme population. However, at this point, no sequence motif has been identified to distinguish cytochrome bd (with a stoichiometric complement of heme d) from an enzyme designated as CIO. Members of the bd-family can be subdivided into those which contain either a long or a short hydrophilic connection between transmembrane helices 6 and 7 in subunit I, designated as the Q-loop. However, it is not clear whether there is a functional consequence of this difference. This review summarizes current knowledge on the physiological functions, genetics, structural and catalytic properties of cytochromes bd. Included in this review are descriptions of the intermediates of the catalytic cycle, the proposed site for the reduction of O2, evidence for a proton channel connecting this active site to the bacterial cytoplasm, and the molecular mechanism by which a membrane potential is generated.

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Kinetics of CO binding to putative Na+‐motive oxidases of the o‐type from Bacillus FTU and of the d‐type from Escherichia coli

Cited by 15 publications

References 18 publications

Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

Microsecond Time-Resolved Absorption Spectroscopy Used to Study CO Compounds of Cytochrome bd from Escherichia coli

Heme–heme and heme–ligand interactions in the di-heme oxygen-reducing site of cytochrome bd from Escherichia coli revealed by nanosecond absorption spectroscopy

The cytochrome bd respiratory oxygen reductases

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