title: Electron transfer in subunit NuoI (TYKY) of Escherichia coli NADH:quinone oxidoreductase (NDH-1).
abstract: Bacterial proton-translocating NADH:quinone oxidoreductase (NDH-1) consists of a peripheral and a membrane domain. The peripheral domain catalyzes the electron transfer from NADH to quinone through a chain of seven iron-sulfur (Fe/S) clusters. Subunit NuoI in the peripheral domain contains two [4Fe-4S] clusters (N6a and N6b) and plays a role in bridging the electron transfer from cluster N5 to the terminal cluster N2. We constructed mutants for eight individual Cys-coordinating Fe/S clusters. With the exception of C63S, all mutants had damaged architecture of NDH-1, suggesting that Cys-coordinating Fe/S clusters help maintain the NDH-1 structure. Studies of three mutants (C63S-coordinating N6a, P110A located near N6a, and P71A in the vicinity of N6b) were carried out using EPR measurement. These three mutations did not affect the EPR signals from [2Fe-2S] clusters and retained electron transfer activities. Signals at g(z) = 2.09 disappeared in C63S and P110A but not in P71A. Considering our data together with the available information, g(z,x) = 2.09, 1.88 signals are assigned to cluster N6a. It is of interest that, in terms of g(z,x) values, cluster N6a is similar to cluster N4. In addition, we investigated the residues (Ile-94 and Ile-100) that are predicted to serve as electron wires between N6a and N6b and between N6b and N2, respectively. Replacement of Ile-100 and Ile-94 with Ala/Gly did not affect the electron transfer activity significantly. It is concluded that conserved Ile-100 and Ile-94 are not essential for the electron transfer.
authors.affiliation: Department of Molecular and Experimental Medicine, MEM-256, The Scripps Research Institute, La Jolla, California 92037.
authors.forename: Prem Kumar
authors.initials: PK
authors.lastname: Sinha
authors.affiliation: Johnson Research Foundation, Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors.forename: Eiko
authors.initials: E
authors.lastname: Nakamaru-Ogiso
authors.affiliation: Department of Molecular and Experimental Medicine, MEM-256, The Scripps Research Institute, La Jolla, California 92037.
authors.forename: Jesus
authors.initials: J
authors.lastname: Torres-Bacete
authors.affiliation: Department of Molecular and Experimental Medicine, MEM-256, The Scripps Research Institute, La Jolla, California 92037.
authors.forename: Motoaki
authors.initials: M
authors.lastname: Sato
authors.affiliation: Department of Molecular and Experimental Medicine, MEM-256, The Scripps Research Institute, La Jolla, California 92037.
authors.forename: Norma
authors.initials: N
authors.lastname: Castro-Guerrero
authors.affiliation: Johnson Research Foundation, Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ohnishi
authors.affiliation: Department of Molecular and Experimental Medicine, MEM-256, The Scripps Research Institute, La Jolla, California 92037.
authors.forename: Akemi
authors.initials: A
authors.lastname: Matsuno-Yagi
authors.affiliation: Department of Molecular and Experimental Medicine, MEM-256, The Scripps Research Institute, La Jolla, California 92037. Electronic address: yagi@scripps.edu.
authors.forename: Takao
authors.initials: T
authors.lastname: Yagi
mesh_terms: D019943:Amino Acid Substitution; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D009243:NAD / Q000235:genetics / Q000378:metabolism*; D009245:NADH Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C540656:NuoH protein, E coli; D009243:NAD; D009245:NADH Dehydrogenase; C479743:NuoL protein, E coli