The phototrophic bacterium Rhodobacter capsulatus contains a single, oxygen-responsive superoxide dismutase (SOD Rc ) homologous to iron-containing superoxide dismutase enzymes. Recombinant SOD Rc , however, displayed higher activity after refolding with Mn 2؉ , especially when the pH of the assay mixture was raised. SOD Rc isolated from Rhodobacter cells also preferentially contains manganese, but metal discrimination depends on the culture conditions, with iron fractions increasing from 7% in aerobic cultures up to 40% in photosynthetic cultures. Therefore, SOD Rc behaves as a Mn-containing dismutase with cambialistic properties.
Challenge of Rhodobacter capsulatus cells with the superoxide propagator methyl viologen resulted in the induction of a diaphorase activity identi¢ed as a member of the ferredoxin (£avodoxin)-(reduced) nicotinamide adenine dinucleotide phosphate (NADP(H)) reductase (FPR) family by N-terminal sequencing. The gene coding for Rhodobacter FPR was cloned and expressed in Escherichia coli. Both native and recombinant forms of the enzyme were puri¢ed to homogeneity rendering monomeric products of V V30 kDa with essentially the same spectroscopic and kinetic properties. They were able to bind and reduce Rhodobacter £avodoxin (NifF) and to mediate typical FPR activities such as the NADPH-driven diaphorase and cytochrome c reductase.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.