Moscoso H, Saavedra C, Loyola C, Pichuantes S, Vásquez C
Laboratorio de Microbiología Molecular, Facultad de Química y Biología, Universidad de Santiago de Chile.
Res Microbiol. 1998 Jun;149(6):389-97. doi: 10.1016/s0923-2508(98)80321-5.
Bacillus stearothermophilus V is a naturally occurring Gram-positive rod which exhibits resistance to potassium tellurite. Crude extracts of this bacterium catalyse the NADH-dependent, protease-sensitive reduction of K2TeO3 in vitro. Two fractions which showed the ability to reduce potassium tellurite (H1 and H2) were obtained. Fraction H1 behaved as a macroaggregate exhibiting a very high molecular mass that could not be estimated accurately. Upon electrophoresis in polyacrylamide gels in the presence of SDS, however, it was resolved into three distinct bands of 60, 41 and 37.5 kDa. On the other hand, an M(r) of 121 was determined for fraction H2 by means of gel filtration and high-pressure liquid chromatography. In SDS-PAGE a unique protein band of 60 kDa was observed, suggesting that it is actually a dimer. Both fractions showed pH and temperature optima of 7.5 and 57 degrees C, respectively. Concentrations of 2.5 M NaCl or 0.35 mM SDS inhibited fraction H2 almost completely, while fraction H1 retained 20% of its activity under the same conditions. Concentrations of 5 mM EDTA caused the activity of both fractions to increase 2-fold. In addition to reducing tellurite, they were also able to reduce Na2SeO3 and Na2SO3 in vitro.
嗜热脂肪芽孢杆菌V是一种天然存在的革兰氏阳性杆菌，对亚碲酸钾具有抗性。该细菌的粗提取物在体外催化依赖于NADH且对蛋白酶敏感的K2TeO3还原反应。获得了两个具有还原亚碲酸钾能力的组分（H1和H2）。组分H1表现为一种高分子质量的大聚集体，其分子量无法准确估算。然而，在SDS存在下于聚丙烯酰胺凝胶中进行电泳时，它被解析为60、41和37.5 kDa的三条明显条带。另一方面，通过凝胶过滤和高压液相色谱法测定组分H2的分子量为121。在SDS-PAGE中观察到一条独特的60 kDa蛋白条带，表明它实际上是一种二聚体。两个组分的最适pH和温度分别为7.5和57℃。2.5 M NaCl或0.35 mM SDS的浓度几乎完全抑制了组分H2，而组分H1在相同条件下保留了其20%的活性。5 mM EDTA的浓度使两个组分的活性增加了2倍。除了还原亚碲酸盐外，它们在体外还能够还原亚硒酸钠和亚硫酸钠。
