Hofbauer Stefan, Gysel Kira, Mlynek Georg, Kostan Julius, Hagmüller Andreas, Daims Holger, Furtmüller Paul G, Djinović-Carugo Kristina, Obinger Christian
University of Natural Resources and Life Sciences, Vienna, Austria.
Biochim Biophys Acta. 2012 Sep;1824(9):1031-8. doi: 10.1016/j.bbapap.2012.05.012. Epub 2012 Jun 6.
Chlorite dismutases (Cld) are unique heme b containing oxidoreductases that convert chlorite to chloride and dioxygen. Recent phylogenetic and structural analyses demonstrated that these metalloproteins significantly differ in oligomeric and subunit structure. Here we have analyzed two representatives of two phylogenetically separated lineages, namely pentameric Cld from Candidatus "Nitrospira defluvii" and dimeric Cld from Nitrobacter winogradskyi having a similar enzymatic activity at room temperature. By application of a broad set of techniques including differential scanning calorimetry, electronic circular dichroism, UV-vis and fluorescence spectroscopy the temperature-mediated and chemical unfolding of both recombinant proteins were analyzed. Significant differences in thermal and conformational stability are reported. The pentameric enzyme is very stable between pH 3 and 10 (T(m)=92°C at pH 7.0) and active at high temperatures thus being an interesting candidate for bioremediation of chlorite. By contrast the dimeric protein starts to unfold already at 53°C. The observed unfolding pathways are discussed with respect to the known subunit structure and subunit interaction.
亚氯酸盐歧化酶（Cld）是一类独特的含血红素b的氧化还原酶，可将亚氯酸盐转化为氯化物和氧气。最近的系统发育和结构分析表明，这些金属蛋白在寡聚体和亚基结构上存在显著差异。在此，我们分析了两个系统发育上分离的谱系的代表，即来自“脱氮硝化螺旋菌（Candidatus 'Nitrospira defluvii'）”的五聚体Cld和来自维诺格拉德斯基硝化杆菌（Nitrobacter winogradskyi）的二聚体Cld，它们在室温下具有相似的酶活性。通过应用包括差示扫描量热法、电子圆二色性、紫外可见光谱和荧光光谱在内的一系列广泛技术，分析了两种重组蛋白的温度介导和化学去折叠过程。报道了热稳定性和构象稳定性的显著差异。五聚体酶在pH 3至10之间非常稳定（在pH 7.0时T(m)=92°C），并且在高温下具有活性，因此是亚氯酸盐生物修复的一个有趣候选物。相比之下，二聚体蛋白在53°C时就开始去折叠。根据已知的亚基结构和亚基相互作用对观察到的去折叠途径进行了讨论。
