The RGSGR amino acid motif of the intercellular signalling protein, HetN, is required for patterning of heterocysts in Anabaena sp strain PCC 7120
The RGSGR amino acid motif of the intercellular signalling protein, HetN, is required for patterning of heterocysts in Anabaena sp strain PCC 7120
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DOI：
10.1111/j.1365-2958.2011.07949.x
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发表时间：
2012-02-01
影响因子：
3.6
通讯作者：
Callahan, Sean M.
中科院分区：
文献类型：
--
作者：
Higa, Kelly C.;Rajagopalan, Ramya;Callahan, Sean M.
在蓝藻鱼腥藻(Anabaena sp.)的菌丝上，固氮异形胞呈周期性排列。在限制结合氮的条件下，菌株PCC7120。图案化需要两种异形胞分化抑制物，PATS和HETN，它们通过横向抑制源细胞邻近细胞中分化激活剂HetR的水平，在不同的分化阶段发挥作用。在这里，我们证明了287个氨基酸的HETN蛋白中的RGSGR序列是图案形成的关键，该序列由PATS共享。这五种氨基酸中的任何一种的保守取代降低了HETN在过度生产时抑制分化的程度，并改变了具有其他野生型遗传背景的细丝中的异形胞的模式。相反，组成这个预测的还原酶的假定催化三联体的氨基酸的取代对抑制或构图没有影响。HETN推测的结构域的缺失表明，RGSGR基序是HETN的主要成分，是其抑制和构图活性所必需的，而异型包囊的构图不需要定位于细胞被膜。细胞间信号蛋白PATS和HETN使用相同的氨基酸基序来调节异胞模式的不同阶段。
Nitrogen-fixing heterocysts are arranged in a periodic pattern on filaments of the cyanobacterium Anabaena sp. strain PCC 7120 under conditions of limiting combined nitrogen. Patterning requires two inhibitors of heterocyst differentiation, PatS and HetN, which work at different stages of differentiation by laterally suppressing levels of an activator of differentiation, HetR, in cells adjacent to source cells. Here we show that the RGSGR sequence in the 287-amino-acid HetN protein, which is shared by PatS, is critical for patterning. Conservative substitutions in any of the five amino acids lowered the extent to which HetN inhibited differentiation when overproduced and altered the pattern of heterocysts in filaments with an otherwise wild-type genetic background. Conversely, substitution of amino acids comprising the putative catalytic triad of this predicted reductase had no effect on inhibition or patterning. Deletion of putative domains of HetN suggested that the RGSGR motif is the primary component of HetN required for both its inhibitory and patterning activity, and that localization to the cell envelope is not required for patterning of heterocysts. The intercellular signalling proteins PatS and HetN use the same amino acid motif to regulate different stages of heterocyst patterning.