Abstract
A mutant of Escherichia coli, unable to produce manganese- or iron-containing superoxide dismutase (SOD), was found to contain modest levels of an SOD that was judged to be a copper- and zinc-containing SOD on the basis of inhibition by cyanide and inactivation by either H2O2 or diethyldithiocarbamate. Moreover, the diethyldithiocarbamate-inactivated enzyme could be reactivated with Cu(II), and this reconstituted enzyme, like the native enzyme, was unaffected by EDTA and was inhibited by cyanide. This enzyme was, furthermore, selectively released by osmotic shock, in keeping with a periplasmic localization, and it was strongly induced during aerobic growth. This enzyme was also present in the SOD-competent parental strain. Failure to detect it previously can be attributed to its periplasmic localization, thermal lability, sensitivity to pH, and to its relative paucity. It will now be interesting to explore the phenotypic consequences imposed by the absence of this SOD.
Highlights
Dithiocarbamate-inactivatedenzymecouldbe reacti- We report that E. coli produce a CuZn.SOD, which is vated with Cu(II), and this reconstituted enzyme, like the native enzyme, was unaffected by EDTA and was inhibited by cyanide
The strains of E. coli used in this work are JI132, which bears insertional defects in the genes coding for both Mn.SODand Fe.SOD, and AB1157, which is the parental strain [12]
The C. crescentis gene desired, was performed in a Coy chamber under 90% N, + 10%Hz
Summary
The strains of E. coli used in this work are JI132, which bears insertional defects in the genes coding for both Mn.SODand Fe.SOD, and AB1157, which is the parental strain [12]. BacteriahavegenerallybeenfoundtocontainFe.SOD’ and/or Mn.SOD; whereas CuZn.SODhas been considered to be lz-amino acids or 0.2%casamino acids at pH 7.4. Anaerobicgrowth, when diminuta a n d Pseudomonas maltophila (31, Caulobacter crescentis (41, Brucella abortus( 5 )and other specieosf Brucella [6], and several speciesof Haemophilus [7]. 22-residue leader sequence was identified [8]. This suggested for SOD activity [17]. In the case of B. abortus the CuZn.SOD-null ap- commercial sources. Peared less able to survive in mice, than was the parental strain, suggestingthat the CuZn.SOD might bea pathogenicity
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