CHARACTERIZATION OF A GENE CONTROLLING HETEROCYST DIFFERENTIATION IN THE CYANOBACTERIUM ANABAENA-7120
CHARACTERIZATION OF A GENE CONTROLLING HETEROCYST DIFFERENTIATION IN THE CYANOBACTERIUM ANABAENA-7120
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DOI：
10.1101/gad.5.2.321
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发表时间：
1991-02-01
影响因子：
10.5
通讯作者：
HASELKORN, R
中科院分区：
文献类型：
--
作者：
BUIKEMA, WJ;HASELKORN, R
鱼腥藻7120突变体216未能分化出异形胞。我们之前发现了一个2.4kb的野生型DNA片段，能够补充这个突变体。我们在这里表明，该片段的序列包含一个单一的开放阅读框架(HetR)，编码一个299个氨基酸的蛋白质。将该片段的缺失亚克隆与216菌株进行接合，结果表明hetR编码区是Het表型互补的必要条件和充分条件。216位的突变位于hetR基因的核苷酸上，将野生型蛋白中179位的丝氨酸转化为突变体中的天冬酰胺。野生型细胞中hetR基因的中断导致了与216相同的突变表型。含有野生型hetR的216细胞和野生型细胞都显示出异形胞的频率增加，即使在含有固定氮的培养基上也是如此。这些结果表明，hetR编码的产物不仅对杂胞体的发育是必要的，而且还控制着杂胞体的发育。这种假定的调节蛋白缺乏已知的转录因子特有的结构基序，并且可能在距离其目标基因一步或几步的水平上发挥作用。
Anabaena 7120 mutant 216 fails to differentiate heterocysts. We previously identified a 2.4-kb wild-type DNA fragment able to complement this mutant. We show here that the sequence of this fragment contains a single open reading frame (hetR), encoding a 299-amino-acid protein. Conjugation of deletion subclones of this fragment into strain 216 showed that the hetR-coding region is both necessary and sufficient for complementation of the Het- phenotype. The mutation in 216 is located at nucleotide 535 in the hetR gene, converting a serine at position 179 in the wild-type protein to an asparagine in the mutant. Interruption of the hetR gene in wild-type cells results in a mutant phenotype identical to that of 216. Both 216 and wild-type cells containing wild-type hetR on a plasmid display increased frequency of heterocysts, even on media containing fixed nitrogen. These results suggest that hetR encodes a product that is not only essential for but also controls heterocyst development. This putative regulatory protein lacks known structural motifs characteristic of transcription factors and probably acts at a level one or more steps removed from its target genes.