Banks G R, Holloman W K, Kairis M V, Spanos A, Yarranton G T
Eur J Biochem. 1976 Feb 2;62(1):131-42. doi: 10.1111/j.1432-1033.1976.tb10106.x.
A DNA polymerase from Ustilago maydis has been purified to apparent homogeneity. The native enzyme possesses a subunit structure consisting of 50000 and 55000-dalton monomers. The apparent sedimentation coefficient of the polymerase activity in the absence of salt is 8.4 S (Mr=180000-200000), that in its presence (0.6 M NaCl or 0.12 M KCl) being 6.3 S (Mr=80000-100000). Low concentrations of EDTA also converted the 8.4-S to a 6.3-S form, whereas magnesium ions catalysed the reverse association. The enzyme has an absolute requirement for both a DNA or RNA template and a DNA primer. For homopolymer templates the primer requirement was satisified by a short complementary oligodeoxynucleotide, but oligoribonucleotides were extremely inefficient primers. With the template-primer poly(dA) X (dT)12, the enzyme added an average of 50 dTMP nucleotides on to each primer molecule, whereas with poly(rA) X (dT)12, this figure was 300. The enzyme also possesses an associated deoxyribonuclease activity. No other DNA polymerase activity was detected in cell-free extracts of U. maydis.
一种来自玉米黑粉菌的DNA聚合酶已被纯化至表观均一。天然酶具有由50000和55000道尔顿单体组成的亚基结构。在无盐条件下，聚合酶活性的表观沉降系数为8.4 S（相对分子质量=180000 - 200000），在有盐存在时（0.6 M NaCl或0.12 M KCl）为6.3 S（相对分子质量=80000 - 100000）。低浓度的EDTA也能将8.4 S的形式转变为6.3 S的形式，而镁离子则催化相反的缔合反应。该酶对DNA或RNA模板以及DNA引物都有绝对需求。对于均聚物模板，引物需求可由短的互补寡聚脱氧核苷酸满足，但寡聚核糖核苷酸作为引物的效率极低。以模板 - 引物聚（dA）×（dT）12为例，该酶在每个引物分子上平均添加50个dTMP核苷酸，而对于聚（rA）×（dT）12，这一数字为300。该酶还具有相关的脱氧核糖核酸酶活性。在玉米黑粉菌的无细胞提取物中未检测到其他DNA聚合酶活性。
