title: Functional roles of four conserved charged residues in the membrane domain subunit NuoA of the proton-translocating NADH-quinone oxidoreductase from Escherichia coli.
abstract: The H(+)(Na(+))-translocating NADH-quinone (Q) oxidoreductase (NDH-1) of Escherichia coli is composed of 13 different subunits (NuoA-N). Subunit NuoA (ND3, Nqo7) is one of the seven membrane domain subunits that are considered to be involved in H(+)(Na(+)) translocation. We demonstrated that in the Paracoccus denitrificans NDH-1 subunit, Nqo7 (ND3) directly interacts with peripheral subunits Nqo6 (PSST) and Nqo4 (49 kDa) by using cross-linkers (Di Bernardo, S., and Yagi, T. (2001) FEBS Lett. 508, 385-388 and Kao, M.-C., Matsuno-Yagi, A., and Yagi, T. (2004) Biochemistry 43, 3750-3755). To investigate the structural and functional roles of conserved charged amino acid residues, a nuoA knock-out mutant and site-specific mutants K46A, E51A, D79N, D79A, E81Q, E81A, and D79N/E81Q were constructed by utilizing chromosomal DNA manipulation. In terms of immunochemical and NADH dehydrogenase activity-staining analyses, all site-specific mutants are similar to the wild type, suggesting that those NuoA site-specific mutations do not significantly affect the assembly of peripheral subunits in situ. In addition, site-specific mutants showed similar deamino-NADH-K(3)Fe(CN)(6) reductase activity to the wild type. The K46A mutation scarcely inhibited deamino-NADH-Q reductase activity. In contrast, E51A, D79A, D79N, E81A, and E81Q mutation partially suppressed deamino-NADH-Q reductase activity to 30, 90, 40, 40, and 50%, respectively. The double mutant D79N/E81Q almost completely lost the energy-transducing NDH-1 activities but did not display any loss of deamino-NADH-K(3)Fe(CN)(6) reductase activity. The possible functional roles of residues Asp-79 and Glu-81 were discussed.
authors.affiliation: Division of Biochemistry, Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Mou-Chieh
authors.initials: MC
authors.lastname: Kao
authors.forename: Salvatore
authors.initials: S
authors.lastname: Di Bernardo
authors.forename: Marta
authors.initials: M
authors.lastname: Perego
authors.forename: Eiko
authors.initials: E
authors.lastname: Nakamaru-Ogiso
authors.forename: Akemi
authors.initials: A
authors.lastname: Matsuno-Yagi
authors.forename: Takao
authors.initials: T
authors.lastname: Yagi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D015153:Blotting, Western; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005822:Genetic Vectors; D018698:Glutamic Acid / Q000737:chemistry; D015151:Immunoblotting; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011522:Protons; D011808:Quinone Reductases / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D019076:Transgenes
chemical_list: D011522:Protons; D001224:Aspartic Acid; D018698:Glutamic Acid; D004247:DNA; C041831:NADH dehydrogenase (quinone); D011808:Quinone Reductases