DEPC modification of the CuA protein from Thermus thermophilus.
J Biol Inorg Chem
; 24(1): 117-135, 2019 02.
Article
en En
| MEDLINE
| ID: mdl-30523412
ABSTRACT
The CuA center is the initial electron acceptor in cytochrome c oxidase, and it consists of two copper ions bridged by two cysteines and ligated by two histidines, a methionine, and a carbonyl in the peptide backbone of a nearby glutamine. The two ligating histidines are of particular interest as they may influence the electronic and redox properties of the metal center. To test for the presence of reactive ligating histidines, a portion of cytochrome c oxidase from the bacteria Thermus thermophilus that contains the CuA site (the TtCuA protein) was treated with the chemical modifier diethyl pyrocarbonate (DEPC) and the reaction followed through UV-visible, circular dichroism, and electron paramagnetic resonance spectroscopies at pH 5.0-9.0. A mutant protein (H40A/H117A) with the non-ligating histidines removed was similarly tested. Introduction of an electron-withdrawing DEPC-modification onto the ligating histidine 157 of TtCuA increased the reduction potential by over 70 mV, as assessed by cyclic voltammetry. Results from both proteins indicate that DEPC reacts with one of the two ligating histidines, modification of a ligating histidine raises the reduction potential of the CuA site, and formation of the DEPC adduct is reversible at room temperature. The existence of the reactive ligating histidine suggests that this residue may play a role in modulating the electronic and redox properties of TtCuA through kinetically-controlled proton exchange with the solvent. Lack of reactivity by the metalloproteins Sco and azurin, both of which contain a mononuclear copper center, indicate that reactivity toward DEPC is not a characteristic of all ligating histidines.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas Bacterianas
/
Thermus thermophilus
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Complejo IV de Transporte de Electrones
/
Dietil Pirocarbonato
/
Histidina
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
J Biol Inorg Chem
Asunto de la revista:
BIOQUIMICA
Año:
2019
Tipo del documento:
Article
País de afiliación:
Estados Unidos