Unusual ring D fixation by three crucial residues promotes phycoviolobilin formation in the DXCF-type cyanobacteriochrome without the second Cys.
Unusual ring D fixation by three crucial residues promotes phycoviolobilin formation in the DXCF-type cyanobacteriochrome without the second Cys.
复制标题
三个关键残基对 D 环的不寻常固定促进了没有第二个 Cys 的 DXCF 型蓝藻色素中藻紫胆素的形成。
DOI：
10.1042/bcj20210013
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
R. Narikawa
中科院分区：
文献类型：
--
作者：
K. Fushimi;R. Narikawa
蓝藻色素是由蓝藻产生的线性四吡咯结合光感受器。它们的发色团结合GAF结构域被划分为许多谱系。其中，在多个谱系中发现了具有高度保守的“第一Cys”和“第二Cys”的双Cys型蓝藻色素GAF结构域。第一个Cys稳定地附着在a环的C31上，而第二个Cys大多与发色团的C10可逆连接。值得注意的是，初级序列中第二个Cys的位置是多样化的，最丰富的双Cys型GAF结构域在DXCF基序中有“第二个Cys”，称为DXCF GAF结构域。人们早就知道，DXCF GAF结构域的第二个Cys不仅表现出可逆的连接，而且参与了从最初掺入的藻蓝胆素到紫胆素的异构化活性（C4=C5双键的还原）。然而，对DXCF GAF结构域AM1_6305g1和AM1_1499g1进行的综合定点突变发现，第二个Cys对于异构化活性是必不可少的，其中三个残基通过固定C环和d环参与了异构化活性。在C5桥的两侧固定发色团是必要的，即使固定位点的一侧远离桥，另一侧在C31由第一个Cys固定。
Cyanobacteriochromes are linear tetrapyrrole-binding photoreceptors produced by cyanobacteria. Their chromophore-binding GAF domains are categorized into many lineages. Among them, dual Cys-type cyanobacteriochrome GAF domains possessing not only a highly conserved "first Cys" but also a "second Cys" are found from multiple lineages. The first Cys stably attaches to C31 of the A-ring, while the second Cys mostly shows reversible ligation to the C10 of the chromophore. Notably, position of the second Cys in the primary sequence is diversified, and the most abundant dual Cys-type GAF domains have a "second Cys" within the DXCF motif, which are called DXCF GAF domains. It has been long known that the second Cys in the DXCF GAF domains not only shows the reversible ligation but also is involved in isomerization activity (reduction of C4=C5 double bond) from the initially incorporated phycocyanobilin to phycoviolobilin. However, comprehensive site-directed mutagenesis on the DXCF GAF domains, AM1_6305g1 and AM1_1499g1, revealed that the second Cys is dispensable for isomerization activity, in which three residues participate by fixing the C- and D-rings. Fixation of the chromophore on both sides of the C5 bridge is necessary, even though one side of the fixation site is far from this bridge, with the other side at C31 fixed by the first Cys.
影响因子：
2.9
作者：
Rockwell, Nathan C.;Njuguna, Stephanie Lane;Spiller, Susan C.
通讯作者：
Spiller, Susan C.