The coordination and function of the redox centres of the membrane-bound nitrate reductases

Under anaerobic conditions and in the presence of nitrate. the facultative anaerobe Escherichia coli synthesises an electron-transport chain comprisin g a primary dehydrogenase and the terminal membrane-bound nitrate reductase A (NarGHI). This review focuses on recent advances obtained on the structu re and function of the three protein subunits of membrane-bound nitrate red uctases. We discuss a global architecture for the Mo-bisMGD-containing subu nit (NarG) and a coordination model for the four [Fe-S] centres of the elec tron-transfer subunit (NarH) and for the two b-type haems of the anchor sub unit NarI.