Maldener I, Lockau W, Cai Y P, Wolk C P
Institut für Botanik, Universität Regensburg, FRG.
Mol Gen Genet. 1991 Jan;225(1):113-20. doi: 10.1007/BF00282649.
It has been suggested that a calcium-dependent intracellular protease of the cyanobacterium, Anabaena sp., participates in the differentiation of heterocysts, cells that are specialized for fixation of N2. Clones of the structural gene (designated prcA) for this protease from Anabaena variabilis strain ATCC 29413 and Anabaena sp. strain PCC 7120 were identified via their expression in Escherichia coli. The prcA gene from A. variabilis was sequenced. The genes of both strains, mutated by insertion of a drug resistance cassette, were returned to these same strains of Anabaena on suicide plasmids. The method of sacB-mediated positive selection for double recombinants was used to achieve replacement of the wild-type prcA genes by the mutated forms. The resulting mutants, which lacked Ca2(+)-dependent protease activity, were not impaired in heterocyst formation and grew on N2 as sole nitrogen source.
有人提出，蓝藻鱼腥藻属的一种钙依赖性细胞内蛋白酶参与异形胞的分化，异形胞是专门用于固定氮气的细胞。通过在大肠杆菌中的表达，鉴定出来自多变鱼腥藻菌株ATCC 29413和鱼腥藻属菌株PCC 7120的这种蛋白酶的结构基因（命名为prcA）的克隆。测定了来自多变鱼腥藻的prcA基因序列。将通过插入耐药盒而发生突变的两种菌株的基因，通过自杀质粒导入到相同的鱼腥藻菌株中。采用sacB介导的双重组体阳性选择方法，用突变形式取代野生型prcA基因。产生的缺乏Ca2(+)依赖性蛋白酶活性的突变体，在异形胞形成方面未受损害，并且能够以氮气作为唯一氮源生长。
