Analysis of Assembly of Complex I and Characterization Of Clinically Identified Mutations In Membrane Subunits ND2, ND4, and ND5, Using an E. coli Model System

Abstract

NADH: ubiquinone oxidoreductase, also known as Complex I, is the first and largest enzyme of the respiratory chain, and has a central role in cellular energy production. We use Complex I from E. coil as a model system, which contains 13 subunits named A‐N. Subunits A, H, J, K, L, M and N, constitute the membrane arm, while the rest of the subunits, B, CD, E, F, G, and I, make up the peripheral arm. The assembly pathway of the bacterial Complex I is uncertain. The assembly pathway of subsets of the membrane subunits has been analyzed by native gel electrophoresis and by co‐immunoprecipitation. A gentle detergent, dodecyl maltoside, was used to extract complexes from cellular membranes. Expression of all subunits leads to a large complex in native gels that appears to be Complex I. Expression of subsets of the membrane subunits leads to formation of sub‐complexes M‐N, J‐K‐M‐N, and A‐H‐J. Subunit L only formed complexes when all subunits were expressed. This question was further addressed by expressing the subunits from 2 different plasmids, simultaneously, or sequentially. In addition several clinically identified mutations in subunits L, M and N (ND5, ND4, and ND2, respectively) were constructed, and analysis by western blotting, native gel electrophoresis, and NADH oxidase activity is underway. In conclusion, E. coli Complex I is an effective model system for studies of assembly and analysis of human mutations.Support or Funding InformationThis work was supported by a NIH grant R15 GM 126507.