THE HGLK GENE IS REQUIRED FOR LOCALIZATION OF HETEROCYST-SPECIFIC GLYCOLIPIDS IN THE CYANOBACTERIUM ANABAENA SP STRAIN PCC-7120
THE HGLK GENE IS REQUIRED FOR LOCALIZATION OF HETEROCYST-SPECIFIC GLYCOLIPIDS IN THE CYANOBACTERIUM ANABAENA SP STRAIN PCC-7120
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DOI：
10.1128/jb.177.22.6440-6448.1995
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发表时间：
1995-11-01
影响因子：
3.2
通讯作者：
HASELKORN, R
中科院分区：
文献类型：
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作者：
BLACK, K;BUIKEMA, WJ;HASELKORN, R
蓝藻Anabaena sp.菌株PCC 7120的突变株543最初被分离为化学诱变后的Fox突变株。超微结构分析表明，在富氮培养基中，突变体的营养细胞比野生型更呈圆柱形，间隔更厚，而在无氮培养基中，突变体的异囊细胞壁外缺乏正常的糖脂层。尽管没有这一层，菌株543的异囊仍然含有异囊特异性糖脂，这是通过薄层色谱测定的。菌株543的突变发生在一个我们命名为hglK的基因上，该基因编码一种由727个氨基酸组成的蛋白质。野生型HglK蛋白似乎包含四个跨膜区域，随后是36个重复的退化五肽序列AXLXX。菌株543的突变在五肽重复区上游引入了一个终止密码子。通过在hglK基因的开头插入抗生素抗性盒构建的突变体具有与菌株543相同的表型。我们提出hglK编码一种蛋白质，这种蛋白质对异囊糖脂的定位是必要的，而这种功能需要hglK蛋白的五肽重复。
Mutant strain 543 of the cyanobacterium Anabaena sp. strain PCC 7120 was originally isolated as a Fox mutant following chemical mutagenesis. Ultrastructural analysis shows that in nitrogen-replete media the vegetative cells of the mutant are more cylindrical acid have thicker septa than those of the wild type, while in nitrogen-free media the mutant heterocysts lack the normal glycolipid layer external to the cell wall. Although this layer is absent, strain 543 heterocysts nevertheless contain heterocyst-specific glycolipids, as determined by thin-layer chromatography. The mutation in strain 543 is in a gene we have named hglK, encoding a protein of 727 amino acids. The wild-type HglK protein appears to contain four membrane-spanning regions followed by 36 repeats of a degenerate pentapeptide sequence, AXLXX. The mutation in strain 543 introduces a termination codon immediately upstream of the pentapeptide repeat region. A mutant constructed by insertion of an antibiotic resistance cassette near the beginning of the hglK gene has the same phenotype as strain 543. We propose that hglK encodes a protein necessary for the localization of heterocyst glycolipids and that this function requires the pentapeptide repeats of the HglK protein.