scholarly journals Transient kinetics of subunit-III-depleted cytochrome c oxidase

1986 ◽  
Vol 234 (3) ◽  
pp. 569-572 ◽  
Author(s):  
F Malatesta ◽  
G Antonini ◽  
P Sarti ◽  
M Brunori
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Flash Photolysis ◽  
Order Rate Constant ◽  
Kinetic Properties ◽  
Transient Kinetics ◽  
Rate Limiting Step ◽  
Subunit Iii ◽  
The Stability ◽  
Rate Limiting

Cytochrome c oxidase from ox heart was depleted of subunit III and its transient kinetic properties studied by stopped-flow and flash photolysis. It was found that the overall mechanism of electron transfer is very similar for subunit-III-depleted and native oxidase, although significant differences in some kinetic parameters have been detected. These include the second-order rate constant for cytochrome c oxidation and the rate-limiting step of the overall process. Moreover, at low cytochrome c/oxidase ratios (where the number of reducing equivalents is insufficient), the rate of reoxidation of cytochrome a was found to be very slow, even in air, and in fact for the subunit-III-depleted enzyme is even slower than for the native oxidase. The stability of reduced cytochrome a excludes the likelihood that removal of subunit III leads to a new O2-binding site, and the result may be relevant to the lowered vectorial H+/e- stoichiometry. The subunit-III-depleted oxidase can be pulsed under appropriate conditions and its combination with CO is unchanged, as shown by kinetic experiments and difference spectroscopy.

scholarly journals Metal-binding mechanism of Cox17, a copper chaperone for cytochrome c oxidase

2004 ◽  
Vol 382 (1) ◽  
pp. 307-314 ◽  
Author(s):  
Peep PALUMAA ◽  
Liina KANGUR ◽  
Anastassia VORONOVA ◽  
Rannar SILLARD
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Metal Binding ◽  
Copper Ions ◽  
Copper Chaperone ◽  
Copper Chaperones ◽  
Rate Limiting Step ◽  
Charge State Distributions ◽  
Rate Limiting ◽  
Partner Proteins

Cox17, a copper chaperone for cytochrome c oxidase, is an essential and highly conserved protein. The structure and mechanism of functioning of Cox17 are unknown, and even its metalbinding stoichiometry is elusive. In the present study, we demonstrate, using electrospray ionization–MS, that porcine Cox17 binds co-operatively four Cu+ ions. Cu4Cox17 is stable at pH values above 3 and fluorescence spectra indicate the presence of a solvent-shielded multinuclear Cu(I) cluster. Combining our results with earlier EXAFS results on yeast CuCox17, we suggest that Cu4Cox17 contains a Cu4S6-type cluster. At supramillimolar concentrations, dithiothreitol extracts metals from Cu4Cox17, and an apparent copper dissociation constant KCu=13 fM was calculated from these results. Charge-state distributions of different Cox17 forms suggest that binding of the first Cu+ ion to Cox17 causes a conformational change from an open to a compact state, which may be the rate-limiting step in the formation of Cu4Cox17. Cox17 binds non-co-operatively two Zn2+ ions, but does not bind Ag+ ions, which highlights its extremely high metal-binding specificity. We further demonstrate that porcine Cox17 can also exist in partly oxidized (two disulphide bridges) and fully oxidized (three disulphide bridges) forms. Partly oxidized Cox17 can bind one Cu+ or Zn2+ ion, whereas fully oxidized Cox17 does not bind metals. The metal-binding properties of Cox17 imply that, in contrast with other copper chaperones, Cox17 is designed for the simultaneous transfer of up to four copper ions to partner proteins. Metals can be released from Cox17 by non-oxidative as well as oxidative mechanisms.

Is the Internal Electron Transfer the Rate-Limiting Step in the Catalytic Cycle of Cytochrome c Oxidase?

1988 ◽  
Vol 550 (1 Cytochrome Ox) ◽  
pp. 161-166 ◽  
Author(s):  
PAOLO SARTI ◽  
GIOVANNI ANTONINI ◽  
RANCESCO MALATESTA ◽  
BEATRICE VALLONE ◽  
MAURIZIO BRUNORI
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Catalytic Cycle ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Internal Electron ◽  
Rate Limiting

Effect of subunit III removal on control of cytochrome c oxidase activity by pH

Biochemistry ◽  
1988 ◽  
Vol 27 (17) ◽  
pp. 6307-6314 ◽  
Author(s):  
Linda C. Gregory ◽  
Shelagh Ferguson-Miller
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Oxidase Activity ◽  
Subunit Iii

Differential expression of cytochrome c oxidase subunit III gene in castes of the termite Reticulitermes santonensis

2006 ◽  
Vol 52 (6) ◽  
pp. 551-557 ◽  
Author(s):  
Marjorie A. Liénard ◽  
Jean-Marc X.S. Lassance ◽  
Ivan Paulmier ◽  
Jean-François Picimbon ◽  
Christer Löfstedt
Keyword(s):  
Cytochrome C ◽  
Differential Expression ◽  
Cytochrome C Oxidase ◽  
Oxidase Subunit ◽  
Reticulitermes Santonensis ◽  
Subunit Iii
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