A MECHANISM FOR COMPLEMENTATION OF THE SODA SODB DEFECT IN ESCHERICHIA-COLI BY OVERPRODUCTION OF THE RBO GENE-PRODUCT (DESULFOFERRODOXIN) FROM DESULFOARCULUS-BAARSII

Overexpression of rbo in Escherichia coli prevents the inactivation of the [4Fe-4S]-containing fumarases that otherwise occurs in the sodA s odB strain, It similarly protects against the increased sensitivity to ward H2O2, which is imposed by the lack of SOD A and SOD B. These resu lts would be explained on the basis of scavenging of O-2(radical anion ) within the cells by RBO. This interpretation was supported by measur ements of intracellular scavenging of O-2(radical anion) by the lucige nin luminescence method. Since SOD activity could not be detected in d ilute extracts, of the RBO-overexpressing sodA sodB strain, we propose that RBO catalyzes the reduction of O-2(radical anion) at the expense of cellular reductants such as NAD(P)H. A similar mechanism may apply to other instances of complementation of SOD defects by non SOD genes .