Features of subunit NuoM (ND4) in Escherichia coli NDH-1: TOPOLOGY AND IMPLICATION OF CONSERVED GLU144 FOR COUPLING SITE 1.

ABSTRACT: The bacterial H(+)-pumping NADH-quinone oxidoreductase (NDH-1) is an L-shaped membrane-bound enzymatic complex. Escherichia coli NDH-1 is composed of 13 subunits (NuoA-N). NuoM (ND4) subunit is one of the hydrophobic subunits that constitute the membrane arm of NDH-1 and was predicted to bear 14 helices. We attempted to clarify the membrane topology of NuoM by the introduction of histidine tags into different positions by chromosomal site-directed mutagenesis. From the data, we propose a topology model containing 12 helices (helices I-IX and XII-XIV) located in transmembrane position and two (helices X and XI) present in the cytoplasm. We reported previously that residue Glu(144) of NuoM was located in the membrane (helix V) and was essential for the energy-coupling activities of NDH-1 (To

SUBMITTER: Torres-Bacete J 

PROVIDER: S-EPMC2785147 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature