Falchuk K H, Mazus B, Ber E, Ulpino-Lobb L, Vallee B L
Biochemistry. 1985 May 7;24(10):2576-80. doi: 10.1021/bi00331a027.
Both the single DNA-dependent RNA polymerase found in zinc-deficient (-Zn) Euglena gracilis and the RNA polymerase III from zinc-sufficient (+Zn) cells have been isolated by methods previously used to purify polymerases I and II [Falchuk, K. H., Mazus, B., Ulpino, L., & Vallee, B. L. (1976) Biochemistry 15, 4468; Falchuk, K. H., Mazus, B., Ulpino, L., & Vallee, B. L. (1977) Biochem. Biophys. Res. Commun. 74, 1206]. Like class II polymerases, the enzyme from -Zn organisms elutes from DNA-cellulose and phosphocellulose with 0.6 M NaCl and 0.35 M NH4Cl, respectively. It is inhibited by 8-hydroxyquinoline, 8-hydroxyquinoline-5-sulfonic acid, alpha,alpha'-bipyridyl, dipicolinic acid, and 1,10-phenanthroline (OP); 4,7-phenanthroline, the nonchelating analogue, does not inhibit. The pKI(OP) of this enzyme is identical with that of polymerase II but distinct from those of polymerases I and III. Elemental analysis confirms that zinc is the functional metal while copper, manganese, iron, and magnesium are absent. However, the -Zn enzyme is at least 4 orders of magnitude more resistant to alpha-amanitin (alpha-A) than the class II polymerase. Further, its response to alpha-A is unlike that of either polymerase I or polymerase III. Thus, -Zn cells contain a single, alpha-amanitin-resistant (alpha-Ar) RNA polymerase, whose behavior otherwise resembles that of the alpha-amanitin-sensitive polymerase II.
在缺锌（-Zn）的纤细裸藻中发现的单一依赖DNA的RNA聚合酶以及来自锌充足（+Zn）细胞的RNA聚合酶III，都已通过先前用于纯化聚合酶I和II的方法分离出来[Falchuk, K. H., Mazus, B., Ulpino, L., & Vallee, B. L. (1976) Biochemistry 15, 4468; Falchuk, K. H., Mazus, B., Ulpino, L., & Vallee, B. L. (1977) Biochem. Biophys. Res. Commun. 74, 1206]。与II类聚合酶一样，来自-Zn生物体的酶分别在0.6 M NaCl和0.35 M NH4Cl条件下从DNA纤维素和磷酸纤维素上洗脱下来。它受到8-羟基喹啉、8-羟基喹啉-5-磺酸、α,α'-联吡啶、二吡啶甲酸和1,10-菲咯啉（OP）的抑制；非螯合类似物4,7-菲咯啉则不抑制。这种酶的pKI(OP)与聚合酶II的相同，但与聚合酶I和III的不同。元素分析证实锌是功能金属，而铜、锰、铁和镁不存在。然而，-Zn酶对α-鹅膏蕈碱（α-A）的抗性至少比II类聚合酶高4个数量级。此外，它对α-A的反应与聚合酶I或聚合酶III的反应不同。因此，-Zn细胞含有一种单一的、对α-鹅膏蕈碱抗性（α-Ar）的RNA聚合酶，其行为在其他方面类似于对α-鹅膏蕈碱敏感的聚合酶II。
