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1.
FEBS Lett ; 580(5): 1350-4, 2006 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-16466722

RESUMO

Heme-copper oxygen reductases catalyze proton translocation across the cellular membrane; this takes place during the reaction of oxygen to water. We demonstrate with attenuated total reflection-Fourier transform infrared (ATR-FTIR) difference spectroscopy that a tyrosine residue of the oxygen reductase from the thermohalophilic Rhodothermus marinus becomes deprotonated in the transition from the oxidized state to the catalytic intermediate ferryl state P(M). This tyrosine residue is most probably Y256, the helix VI tyrosine residue proposed to substitute for the D-channel glutamic acid that is absent in this enzyme. Comparison with the mitochondrial like oxygen reductase from Rhodobacter sphaeroides suggests that proton transfer from a strategically situated donor to the active site is a crucial step in the reaction mechanism of oxygen reductases.


Assuntos
Citocromos a3/metabolismo , Oxigênio/metabolismo , Rhodothermus/enzimologia , Tirosina/química , Sítios de Ligação , Catálise , Oxirredução , Oxirredutases , Prótons , Rhodobacter sphaeroides/enzimologia , Rhodothermus/metabolismo , Espectroscopia de Infravermelho com Transformada de Fourier
2.
Chembiochem ; 5(4): 431-6, 2004 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-15185365

RESUMO

The catalytic action of membrane proteins is vital to many cellular processes. Yet the molecular mechanisms remain poorly understood. We describe here the technique of evanescent infrared difference spectroscopy as a tool to decipher the structural changes associated with the enzymatic action of membrane proteins. Functional changes as minute as the protonation state of individual amino acid side chains can be observed and linked to interactions with a ligand, agonist, effector, or redox partner.


Assuntos
Proteínas de Membrana/química , Espectrofotometria Infravermelho/métodos , Bacteriorodopsinas/química , Bacteriorodopsinas/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/química , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Proteínas de Membrana/metabolismo , Rodopsina/química , Rodopsina/metabolismo
3.
Proc Natl Acad Sci U S A ; 100(15): 8715-20, 2003 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-12851460

RESUMO

Cytochrome c oxidase, the terminal protein in the respiratory chain, converts oxygen into water and helps generate the electrochemical gradient used in the synthesis of ATP. The catalytic action of cytochrome c oxidase involves electron transfer, proton transfer, and O2 reduction. These events trigger specific molecular changes at the active site, which, in turn, influence changes throughout the protein, including alterations of amino acid side chain orientations, hydrogen bond patterns, and protonation states. We have used IR difference spectroscopy to investigate such modulations for the functional intermediate states E, R2,Pm, and F. These spectra reveal deprotonation of its key glutamic acid E286 in the E and in the Pm states. The consecutive deprotonation and reprotonation of E286 twice within one catalytic turnover illustrates the role of this residue as a proton shuttle. In addition, the spectra point toward deprotonation of a redox-active tyrosine, plausibly Y288, in the F intermediate. Structural insights into the molecular mechanism of catalysis based on the subtle molecular changes observed with IR difference spectroscopy are discussed.


Assuntos
Complexo IV da Cadeia de Transporte de Elétrons/química , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Rhodobacter sphaeroides/enzimologia , Fenômenos Biofísicos , Biofísica , Monóxido de Carbono/química , Catálise , Transporte de Elétrons , Complexo IV da Cadeia de Transporte de Elétrons/genética , Ácido Glutâmico/química , Modelos Moleculares , Mutagênese Sítio-Dirigida , Oxirredução , Conformação Proteica , Prótons , Rhodobacter sphaeroides/genética , Espectrofotometria Infravermelho
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