INVESTIGADORES
DALOSTO sergio Daniel
artículos
Título:
Heterologous production and functional characterization of Bradyrhizobium japonicum copper-containing nitrite reductase and its physiological redox partner cytochrome c550
Autor/es:
CRISTALDI, JULIO C.; FERRONI, FELIX; DURÉ, ANDREA; RAMIREZ, CINTIA; DALOSTO, SERGIO; RIZZI, ALBERTO C; GONZALEZ, PABLO; RIVAS, MARIA GABRIELA; BRONDINO, CARLOS D.
Revista:
METALLOMICS
Editorial:
ROYAL SOC CHEMISTRY
Referencias:
Lugar: CAMBRIDGE; Año: 2020 vol. 12 p. 2084 - 2097
ISSN:
1756-5901
Resumen:
Two domain copper-nitrite reductases (NirK) contain two types of copper centers, one electron transfer (ET) center of type 1 (T1) and a catalytic site of type 2 (T2). NirK activity is pH-dependent, which has been suggested to be produced by structural modifications at high pH of some catalytically relevant residues. To characterize the pH-dependent kinetic of NirK and the relevance of T1 covalency in intraprotein ET, we studied the biochemical, electrochemical, and spectroscopic properties complemented with QM/MM calculations of Bradyrhizobium japonicum NirK (BjNirK) and of its electron donor cytochrome c550 (BjCycA). BjNirK presents absorption spectra determined mainly by a S(Cys)3p→Cu2+ ligand-to-metal charge-transfer (LMCT) transition. The enzyme shows low activity likely due to the higher flexibility of a protein loop associated with BjNirK/BjCycA interaction. Nitrite is reduced at high pH in a T1-decoupled way without T1→T2 ET in which proton delivery for nitrite reduction at T2 is maintained. Our results are analyzed in comparison with previous results found by us in Sinorhizobium meliloti NirK, whose main UV-vis absorption features are determined by S(Cys)3p/→Cu2+ LMCT transitions.