Sorger G J, Trofimenkoff D
Proc Natl Acad Sci U S A. 1970 Jan;65(1):74-80. doi: 10.1073/pnas.65.1.74.
Mutants of Azotobacter which grow normally on excess ammonia under a variety of conditions and which grow slowly or not at all on atmospheric nitrogen have been isolated. Extracts of these strains have low or no detectable nitrogenase activity. There are three classes of mutants. Cell-free preparations of members of the first class possess an enhancement factor (EF+) which stimulates wild-type nitrogenase in vitro. Homogenates of members of the second class possess an enhanceable factor (EF-) which complements in vitro with extracts of the first class of mutants to give substantial nitrogenase activity. Preparations of members of the third class contain neither EF+ nor EF- activity. EF+ and EF- are repressed by the same conditions that repress nitrogenase. Molybdenum-deficient cells of the second class of mutants do not appear to contain EF- activity, but molybdenum deficient cells of the first class of mutants contain EF+. Because of these observations, EF+ is tentatively equated to azoferredoxin and EF- to molybdoferredoxin.
已分离出一些固氮菌突变体，它们在多种条件下的过量氨中能正常生长，但在大气氮中生长缓慢或根本不生长。这些菌株的提取物具有低的或无法检测到的固氮酶活性。有三类突变体。第一类成员的无细胞制剂具有一种增强因子（EF+），它在体外刺激野生型固氮酶。第二类成员的匀浆具有一种可增强因子（EF-），它在体外与第一类突变体的提取物互补，以产生大量的固氮酶活性。第三类成员的制剂既不含有EF+活性也不含有EF-活性。EF+和EF-受到与抑制固氮酶相同条件的抑制。第二类突变体的缺钼细胞似乎不含有EF-活性，但第一类突变体的缺钼细胞含有EF+。基于这些观察结果，暂时将EF+等同于偶氮铁氧化还原蛋白，将EF-等同于钼铁氧化还原蛋白。
