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

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).