A Ligand-Exchange Mechanism of Proton Pumping Involving Tyrosine-422 of Subunit I of Cytochrome Oxidase Is Ruled Out†

Biochemistry ◽  
1996 ◽  
Vol 35 (3) ◽  
pp. 824-828 ◽  
Author(s):  
David M. Mitchell ◽  
Pia Ädelroth ◽  
Jonathan P. Hosler ◽  
John R. Fetter ◽  
Peter Brzezinski ◽  
...  
Keyword(s):  
Cytochrome Oxidase ◽  
Ligand Exchange ◽  
Proton Pumping ◽  
Exchange Mechanism

Theoretical Study of the Energetics of Proton Pumping and Oxygen Reduction in Cytochrome Oxidase

2003 ◽  
Vol 107 (39) ◽  
pp. 10946-10955 ◽  
Author(s):  
Per E. M. Siegbahn ◽  
Margareta R. A. Blomberg ◽  
Mattias L. Blomberg
Keyword(s):  
Oxygen Reduction ◽  
Cytochrome Oxidase ◽  
Theoretical Study ◽  
Proton Pumping

A Proton Magnetic Resonance Study of Ligand Exchange on Tetrakis(tetramethylthiourea)zinc(II) Ion

1979 ◽  
Vol 32 (9) ◽  
pp. 1915 ◽  
Author(s):  
MN Tkaczuk ◽  
SF Lincoln
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Time Scale ◽  
Ligand Exchange ◽  
Proton Magnetic Resonance ◽  
Exchange Mechanism ◽  
Magnetic Resonance Study ◽  
Fast Exchange ◽  
Proton Magnetic Resonance Study

The rate of ligand exchange on the tetrakis(tetramethylthiourea) zinc(II) ion, determined by 1H N.M.R. methods, in CD2Cl2 solution is found to be independent of free-tetramethylthiourea concentration. This is consistent with a dissociative ligand-exchange mechanism being operative. Typically for a solution in which [Zn{S=C(NMe2)2}42+] and [S=C(NMe2)2] were 0�00101 and 0�00376 respectively, kex(200 K) = 16�0�0.6 s-1, ΔH‡ = 64�9�O.8 kJ mol-1 and ΔS‡ = 106�4 J K-1 mol-1 where the observed ligand-exchange rate is given by rate = 4kex[Zn {S=C(NMe2)2}42+] The preparations of [Zn(O=CHNMe2)6](ClO4)2, [Zn{O=CMe(NMe2)}6](Cl04)2, and [Zn{O=C- (NMe2)2}4](ClO4)2 are also reported. The rate of ligand exchange upon these three species in CD2Cl2 solution was found to be in the fast-exchange limit of the N.M.R. time scale.

Effect of diethyl pyrocarbonate modification on spectral and steady-state kinetic properties of bovine heart cytochrome oxidase

1992 ◽  
Vol 70 (7) ◽  
pp. 565-572
Author(s):  
John D. Doran ◽  
Bruce C. Hill
Keyword(s):  
Electron Transfer ◽  
Steady State ◽  
Cytochrome Oxidase ◽  
Proton Pumping ◽  
Kinetic Properties ◽  
High Turnover ◽  
Bovine Heart ◽  
Diethyl Pyrocarbonate ◽  
Steady State Kinetic ◽  
State Kinetic

The histidine-specific reagent diethyl pyrocarbonate has been used to chemically modify bovine heart cytochrome oxidase. Thirty-two of sixty-seven histidine residues of cytochrome oxidase are accessible to modification by diethyl pyrocarbonate. Effects on the Soret and α bands of the heme spectrum indicate disturbance in the environment of one or both of the heme groups. However, diethyl pyrocarbonate modification does not alter the 830-nm absorbance band, suggesting that the environment of CuA is unchanged. Maximal modification of cytochrome oxidase by diethyl pyrocarbonate results in loss of 85–90% of the steay-state electron transfer activity, which can be reversed by hydroxylamine treatment. However, modification of the first 20 histidines does not alter either activity or the heme spectrum, but only when 32 residues have been modified are the activity and heme spectral changes complete. The steady-state kinetic profile of fully modified oxidase is monophasic; the phase corresponding to tight cytochrome c binding and low turnover is retained, whereas the high turnover phase is abolished. Proteoliposomes incorporated with modified oxidase have a 65% lower respiratory control ratio and 40% lower proton pumping stoichiometry than liposomes containing unmodified oxidase. These results are discussed in terms of a redox-linked proton pumping model for energy coupling via cytochrome oxidase.Key words: cytochrome oxidase, histidine modification, electron transfer, proton pumping, diethyl pyrocarbonate.

Ligand exchange mechanism of fac-[99mTc(CO)3(H2O)3]+ complex for 99mTc-CO-MIBI radiopharmaceuticals

2010 ◽  
Vol 37 (6) ◽  
pp. 704
Author(s):  
Li-Hai Yu ◽  
De-Cai Fang ◽  
Hui-Ying Ren ◽  
Hong-Mei Jia ◽  
Bo-Li Liu
Keyword(s):  
Ligand Exchange ◽  
Exchange Mechanism

The Structure of cbb3 Cytochrome Oxidase Provides Insights into Proton Pumping

Science ◽  
2010 ◽  
Vol 329 (5989) ◽  
pp. 327-330 ◽  
Author(s):  
S. Buschmann ◽  
E. Warkentin ◽  
H. Xie ◽  
J. D. Langer ◽  
U. Ermler ◽  
...  
Keyword(s):  
Cytochrome Oxidase ◽  
Proton Pumping

A proton magnetic resonance study of ligand exchange on tetrakis(N,N-diethylacetamide)beryllium(II)

1982 ◽  
Vol 35 (8) ◽  
pp. 1555 ◽  
Author(s):  
MN Tkaczuk ◽  
SF Lincoln
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Ligand Exchange ◽  
Proton Magnetic Resonance ◽  
Exchange Mechanism ◽  
Magnetic Resonance Study ◽  
Rate Law ◽  
Proton Magnetic Resonance Study ◽  
Exchange Data

A lH n.m.r. study shows that ligand exchange on tetrakis(N,N-diethylacetamide)beryllium(II) in both CD3NO2 and CD3CN solution is charaterized by the rate law: Exchange rate = 4(k1 + k2[OCMe(NEt2)]free)[Be{OCMe(NEt2)}42+] In CD3NO2 solution k1 (340K) is 2.3 � 0.1 s-1, ΔH‡.76.4 � 2.2 kJ mol-1, ΔS‡ -14.6 � 6.4 JK-1 mol-1, k2 (340K) 19.9 � 0.3 dm3 mol-1s-1, ΔH‡ 68.5 � 0.8kJ mol-1, ΔS‡ -19.6 � 2.4 JK-1 mol-1, and somewhat different magnitudes are observed in CD3CN solution. The k1 term is assigned to a dissociative (D) ligand exchange mechanism, and the k2 term is assigned to either an associative (A) or an interchange (I) mechanism. These data are discussed in conjunction with ligand exchange data for other beryllium(II) systems.

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