Anaerobic Respiration - Exercise #1- Advanced

You are interested in the role of NADH dehydrogenase in anaerobic respiration. The genome of E. coli encodes for two NADH dehydrogenases, NDH-1 and NDH-2. 

  1. Since NDH-1 is a protein complex embedded in the cytoplasmic membrane, it has a hydrophobic component.  Name the subunit composition of the hydrophobic fragment and point out which of these subunits binds the ubiquinone molecules.


  2. Name two protein(s)/molecule(s) that regulate gene expression of the NDH-2 operon.


  3. NDH-1 is used during anaerobic respiration to oxidize NADH and fumarate can act as the terminal electron acceptor.  Observing the enzymatic reaction carried out by fumarate reductase, what is fumarate reduced to?  Does this result in any direct proton translocation to the periplasm by the reductase? 

  5. NDH-1 and NDH-2 catalyze the transfer of electrons into the quinone pool.  Do both complexes contribute to the electrochemical gradient?  Explain your answer.