Differences in enzymatic properties allow SodCI but not SodCII to contribute to virulence in Salmonella enterica serovar typhimurium strain 14028
Differences in enzymatic properties allow SodCI but not SodCII to contribute to virulence in Salmonella enterica serovar typhimurium strain 14028
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DOI：
10.1128/jb.186.16.5230-5238.2004
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发表时间：
2004-08-01
影响因子：
3.2
通讯作者：
Slauch, JM
中科院分区：
文献类型：
--
作者：
Krishnakumar, R;Craig, M;Slauch, JM
鼠伤寒沙门氏菌产生两种Cu/Zn辅因子周质超氧化物歧化酶，SodCI和SodCII。虽然sodCI中的突变使毒力减弱八倍，但SodCII的缺失不赋予毒力表型，也不增强在sodCI背景中观察到的缺陷。尽管存在这种体内表型，但SodCI和SodCII在生长的稳定期期间在体外以相似的水平表达。通过交换sodCI和sodCII的开放阅读框，我们发现当置于sodCII启动子的控制下时，SodCI有助于毒力。相比之下，SodCII即使从sodCI启动子表达也不有助于毒力。因此，毒力表型的差异主要是由于两种酶之间的一些物理差异。在试图确定SodCI的独特属性，我们已经测试了可能影响吞噬体内酶活性的因素。我们发现，SodCI和SodCII在其耐酸性、耐过氧化氢性或在铜限制环境中获得铜的能力方面没有显著差异。这两种酶在没有铜的情况下合成为脱辅基酶，并且当加入铜时可以完全再金属化。我们注意到的一个显著差异是，SodCII通常通过渗透压休克释放，而SodCI通过明显的非共价相互作用“束缚”在周质内。我们建议，这种新的属性的SodCI是至关重要的，其能力，有助于毒力鼠伤寒血清型。
Salmonella enterica serovar Typhimurium produces two Cu/Zn cofactored periplasmic superoxide dismutases, SodCI and SodCII. While mutations in sodCI attenuate virulence eightfold, loss of SodCII does not confer a virulence phenotype, nor does it enhance the defect observed in a sodCI background. Despite this in vivo phenotype, SodCI and SodCII are expressed at similar levels in vitro during the stationary phase of growth. By exchanging the open reading frames of sodCI and sodCII, we found that SodCI contributes to virulence when placed under the control of the sodCII promoter. In contrast, SodCII does not contribute to virulence even when expressed from the sodCI promoter. Thus, the disparity in virulence phenotypes is due primarily to some physical difference between the two enzymes. In an attempt to identify the unique property of SodCI, we have tested factors that might affect enzyme activity inside a phagosome. We found no significant difference between SodCI and SodCII in their resistance to acid, resistance to hydrogen peroxide, or ability to obtain copper in a copper-limiting environment. Both enzymes are synthesized as apoenzymes in the absence of copper and can be fully remetallated when copper is added. The one striking difference that we noted is that, whereas SodCII is released normally by an osmotic shock, SodCI is "tethered" within the periplasm by an apparently noncovalent interaction. We propose that this novel property of SodCI is crucial to its ability to contribute to virulence in serovar Typhimurium.