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Literature summary for 1.7.5.1 extracted from

  • Zhao, Z.; Rothery, R.A.; Weiner, J.H.
    Effects of site-directed mutations on heme reduction in Escherichia coli nitrate reductase A by menaquinol: a stopped-flow study (2003), Biochemistry, 42, 14225-14233.
    View publication on PubMed
Search for more literature for 1.7.5.1

Protein Variants

Protein Variants Comment Organism
H187Y mutant lacking heme bL but having heme bH, the heme reduction by menadiol is abolished Escherichia coli
H205Y mutant without heme bH but with heme bL, a smaller and slower heme reduction compared to that of the wild-type enzyme is observed. A transient species, likely to be associated with a semiquinone radical anion, is generated not only on reduction of the wild-type enzyme but also on reduction of NarGHIH56R and NarGHIH205Y. Compared to the wild type, no significant heme reoxidation is observed for NarGHIH56R and NarGHIH205Y. This result indicates that a single mutation removing heme bH blocks the electron-transfer pathway from the subunit NarI to the catalytic dimer NarGH Escherichia coli
H56R mutant without heme bH but with heme bL, a smaller and slower heme reduction compared to that of the wild-type enzyme is observed. A transient species, likely to be associated with a semiquinone radical anion, is generated not only on reduction of the wild-type enzyme but also on reduction of NarGHIH56R and NarGHIH205Y. Compared to the wild type, no significant heme reoxidation is observed for NarGHIH56R and NarGHIH205Y. This result indicates that a single mutation removing heme bH blocks the electron-transfer pathway from the subunit NarI to the catalytic dimer NarGH Escherichia coli
H66Y mutant lacking heme bL but having heme bH, the heme reduction by menadiol is abolished Escherichia coli

Inhibitors

Inhibitors Comment Organism Structure
2-n-heptyl-4-hydroxyquinoline N-oxide has significant effects on the reduction kinetics of NarGHIH56R and NarGHIH205Y Escherichia coli
Stigmatellin has significant effects on the reduction kinetics of NarGHIH56R and NarGHIH205Y Escherichia coli

Organism

Organism UniProt Comment Textmining
Escherichia coli
-
-
-

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
nitrate + 2-methyl-1,4-naphthoquinol i.e. menadiol. Electrons from menadiol oxidation are transferred initially to heme bL Escherichia coli nitrite + 2-methyl-1,4-naphthoquinone + H2O
-
 ?

Synonyms

Synonyms Comment Organism
NarGHI
-
 Escherichia coli
nitrate reductase A
-
 Escherichia coli

Cofactor

Cofactor Comment Organism Structure
cytochrome bH both heme bL and heme bH are crucial components in the electron-transfer pathway from the subunit NarI through subunit NarH to the catalytic subunit NarG. Without heme bL electrons cannot be transferred from menaquinol to heme bH. On the other hand, in the absence of heme bH, electrons cannot be transferred from the reduced heme bL to the catalytic dimer NarGH. A complex of menadione radical anion associated with the enzyme, is formed during the process of heme reduction by menadiol Escherichia coli
cytochrome bL both heme bL and heme bH are crucial components in the electron-transfer pathway from the subunit NarI through subunit NarH to the catalytic subunit NarG. Without heme bL electrons cannot be transferred from menaquinol to heme bH. On the other hand, in the absence of heme bH, electrons cannot be transferred from the reduced heme bL to the catalytic dimer NarGH. A complex of menadione radical anion associated with the enzyme, is formed during the process of heme reduction by menadiol Escherichia coli