Biochemistry and Genetics of Nitrate Reductase in Bacteria

Abstract

Publisher Summary The chapter focuses on the biochemistry and genetics of nitrate reductase in bacteria. Nitrate reductase has been shown to be an enzyme composed of various subunits. The enzyme can be isolated in different forms—depending on the method used for its solubilization, it may be isolated with a different number of units and as a monomer, dimer, or tetramer. Nitrate reductase is a non-haem iron protein, containing molybdenum. Furthermore, it is clear that several genes are involved in the formation and the attachment of the molybdenum-containing cofactor to the nitrate reductase apoprotein. The reconstitution of active nitrate reductase seems promising for the identification of the nature of this cofactor. This is not only of importance for our understanding of the role of molybdenum in the nitrate reductase reaction. No molybdenum containing cofactor has been identified with any molybdoprotein. The occurrence of various subunits seems to be a general property of membrane proteins, and the same has been found for formate dehydrogenase, tetrathionate reductase, and ATPase. The reconstitution of active nitrate reductase, by mixing extracts of chl A and chl B mutants of E. coli, is very interesting. It is evident that the studies on the incorporation of proteins and lipids into the reconstituted particles may have a great similarity to the normal process, which membrane-bound enzymes undergo during biosynthesis and assembly in vivo. Therefore this system holds great promise for our future understanding of membrane assembly.