TY - JOUR
T1 - Electron transfer and docking between cytochrome cd1 nitrite reductase and different redox partners - A comparative study
AU - Pedroso, Humberto A.
AU - Silveira, Célia M.
AU - Almeida, Rui M.
AU - Almeida, Ana
AU - Besson, Stéphane
AU - Moura, Isabel
AU - Moura, José J.G.
AU - Almeida, M. Gabriela
N1 - Publisher Copyright:
© 2016 Elsevier B.V. All rights reserved.
PY - 2016/9/1
Y1 - 2016/9/1
N2 - Cytochrome cd1 nitrite reductases (cd1NiRs) catalyze the reduction of nitrite to nitric oxide in denitrifying bacteria, such as Marinobacter hydrocarbonoclasticus. Previous work demonstrated that the enzymatic activity depends on a structural pre-activation triggered by the entry of electrons through the electron transfer (ET) domain, which houses a heme c center. The catalytic activity of M. hydrocarbonoclasticus cd1NiR (Mhcd1NiR) was tested by mediated electrochemistry, using small ET proteins and chemical redox mediators. The rate of enzymatic reaction depends on the nature of the redox partner, with cytochrome (cyt) c552 providing the highest value. In situations where cyt c552 is replaced by either a biological (cyt c from horse heart) or a chemical mediator the catalytic response was only observed at very low scan rates, suggesting that the intermolecular ET rate is much slower. Molecular docking simulations with the 3D model structure of Mhcd1NiR and cyt c552 or cyt c showed that hydrophobic interactions favor the formation of complexes where the heme c domain of the enzyme is the principal docking site. However, only in the case of cyt c552 the preferential areas of contact and Fe-Fe distances between heme c groups of the redox partners allow establishing competent ET pathways. The coupling of the enzyme with chemical redox mediators was also found not to be energetically favorable. These results indicate that although low activity functional complexes can be formed between Mhcd1NiR and different types of redox mediators, efficient ET is only observed with the putative physiological electron donor cyt c552.
AB - Cytochrome cd1 nitrite reductases (cd1NiRs) catalyze the reduction of nitrite to nitric oxide in denitrifying bacteria, such as Marinobacter hydrocarbonoclasticus. Previous work demonstrated that the enzymatic activity depends on a structural pre-activation triggered by the entry of electrons through the electron transfer (ET) domain, which houses a heme c center. The catalytic activity of M. hydrocarbonoclasticus cd1NiR (Mhcd1NiR) was tested by mediated electrochemistry, using small ET proteins and chemical redox mediators. The rate of enzymatic reaction depends on the nature of the redox partner, with cytochrome (cyt) c552 providing the highest value. In situations where cyt c552 is replaced by either a biological (cyt c from horse heart) or a chemical mediator the catalytic response was only observed at very low scan rates, suggesting that the intermolecular ET rate is much slower. Molecular docking simulations with the 3D model structure of Mhcd1NiR and cyt c552 or cyt c showed that hydrophobic interactions favor the formation of complexes where the heme c domain of the enzyme is the principal docking site. However, only in the case of cyt c552 the preferential areas of contact and Fe-Fe distances between heme c groups of the redox partners allow establishing competent ET pathways. The coupling of the enzyme with chemical redox mediators was also found not to be energetically favorable. These results indicate that although low activity functional complexes can be formed between Mhcd1NiR and different types of redox mediators, efficient ET is only observed with the putative physiological electron donor cyt c552.
KW - Cytochrome c
KW - Cytochrome cd nitrite reductase
KW - Electronic pathways
KW - Intermolecular electron transfer
KW - Mediated electrochemistry
KW - Molecular coupling
UR - http://www.scopus.com/inward/record.url?scp=84974603879&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2016.04.279
DO - 10.1016/j.bbabio.2016.04.279
M3 - Article
C2 - 27133504
AN - SCOPUS:84974603879
SN - 0005-2728
VL - 1857
SP - 1412
EP - 1421
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 9
ER -