The Single Superoxide Dismutase of Rhodobacter capsulatus Is a Cambialistic, Manganese-Containing Enzyme

Abstract

ABSTRACT 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.