Stimulation of Mn2+Oxidation inLeptothrix discophoraSS-1 by Cu2+and Sequence Analysis of the Region Flanking the Gene Encoding Putative Multicopper Oxidase MofA

Abstract The effect of Cu2+ on the Mn2+-oxidizing activity secreted by Leptothrix discophora strain SS-1 was studied. Cu2+ stimulated the activity of spent medium from stationary cultures when added during growth of the bacteria, although cell yield decreased with increasing Cu2+ concentrations. The stimulation was tentatively explained by involvement of the putative multicopper oxidase MofA in Mn2+ oxidation. Cu2+ did not enhance the activity when added directly to spent medium, possibly because the ions had to be incorporated during synthesis of the oxidizing factor. Sequence analysis of the region downstream from the mofA gene resulted in identification of mofB, which encodes a protein with a potential peptidyl-prolyl-cis-trans isomerase site, and mofC, which encodes a protein with a potential heme-binding site. The possibility that mofA, mofB, and mofC belong to one operon, and the possible functions of MofB and MofC, are discussed. Keywords: Cu2;Leptothrix Discophora;Mof Operon;Mn2 Oxidation;Multicopper Oxidase Mofa