Journal of Bioenergetics and Biomembranes

, Volume 42, Issue 6, pp 511-516

First online:

Transmembrane topology of subunit N of complex I (NADH:ubiquinone oxidoreductase) from Escherichia coli

  • Bilal AmarnehAffiliated withDepartment of Biological Sciences, Southern Methodist UniversityDepartment of Molecular Genetics, University of Texas Southwestern Medical Center
  • , Steven B. VikAffiliated withDepartment of Biological Sciences, Southern Methodist University Email author 

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The transmembrane topology of subunit N from E. coli Complex I has been investigated. Chemical labeling of mono-substituted cysteine mutants was carried out in inverted membrane vesicles, and in whole cells, using 3-N-maleimidyl-propionyl biocytin (MPB). The results support a model of 14 transmembrane spans with both termini in the periplasm, and are consistent with the models of subunits L, M and N from the crystal structure of the membrane arm of the E. coli Complex I (Efremov et al. (2010) Nature 465, 441–445). In particular, the results do not support an unusual cytoplasmic localization of two likely transmembrane regions, as proposed in previous studies (Mathiesen and Hägerhäll (2002) Biochim Biophys Acta 1556, 121–132; Torres-Bacete, et al. (2009) J Biol Chem 284, 33062–33069).


Complex I NADH:ubiquinone oxidoreductase Transmembrane topology Cysteine mutagenesis Chemical labeling 3-N-maleimidyl-propionyl biocytin