Dimerization properties of the RpBphP2 chromophore-binding domain crystallized by homologue-directed mutagenesis
Dimerization properties of the RpBphP2 chromophore-binding domain crystallized by homologue-directed mutagenesis
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DOI：
10.1107/s0907444912020537
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发表时间：
2012-08-01
期刊：
影响因子：
--
通讯作者：
Papiz, Miroslav Z.
中科院分区：
文献类型：
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作者：
Bellini, Dom;Papiz, Miroslav Z.
细菌光敏色素（BphPs）是含有胆绿素IX α的光感受器，其在红色（Pr）和远红色（Pfr）吸收状态之间进行光转换。BphPs是双组分系统的一半，其将光信号传递到组氨酸激酶结构域，然后传递到基因应答调节剂。在沼泽红球藻中，捕光复合物（LH 4）的合成由两个BphPs（RpBphP 2和RpBphP 3）控制。尽管它们的序列同一性很高（52%），但它们的吸收光谱非常不同。RpBphP 2的光谱表现出经典的Pr-至-Pfr光转化，而RpBphP 3猝灭并出现高能Pnr状态[Giraud等人（2005），J. Biol. Chem. 280，32389-32397]。RpBphP 2的发色团结合结构域（CBD）（RpBphP 2-CBD）的结晶被证明是困难的，并且RpBphP 3-CBD的结构被用于使用同源定向诱变使RpBphP 2-CBD* 结晶。结构表明，二聚化是RpBphP 2-CBD* 成功结晶的重要因素，并由N136 R突变引起。该位点的突变与其他截短的BphPs的二聚化能力相关，也可能对全长二聚体的形成很重要。RpBphP 3-CBD和RpBphP 2-CBD* 胆绿素IX α口袋的比较显示，前者在B和D吡咯环周围具有额外的氢键，这可能限制光转化为Pfr，导致应变的光激发Pnr状态。
Bacteriophytochromes (BphPs) are biliverdin IX alpha-containing photoreceptors that photoconvert between red (Pr) and far-red (Pfr) absorbing states. BphPs are one half of a two-component system that transmits a light signal to a histidine kinase domain and then to a gene-response regulator. In Rhodopseudomonas palustris, synthesis of a light-harvesting complex (LH4) is controlled by two BphPs (RpBphP2 and RpBphP3). Despite their high sequence identity (52%), their absorption spectra are very different. The spectra of RpBphP2 exhibit classic Pr-to-Pfr photoconversion, whereas RpBphP3 quenches and a high-energy Pnr state emerges [Giraud et al. (2005), J. Biol. Chem. 280, 32389-32397]. Crystallization of the chromophore-binding domain (CBD) of RpBphP2 (RpBphP2-CBD) proved to be difficult and the structure of RpBphP3-CBD was used to crystallize RpBphP2-CBD* using homologue-directed mutagenesis. The structure shows that dimerization is an important factor in successful crystallization of RpBphP2-CBD* and arises from an N136R mutation. Mutations at this site correlate with an ability to dimerize in other truncated BphPs and may also be important for full-length dimer formation. Comparison of the RpBphP3-CBD and RpBphP2-CBD* biliverdin IX alpha pockets revealed that the former has additional hydrogen bonding around the B and D pyrrole rings that may constrain photoconversion to Pfr, resulting in a strained photoexcited Pnr state.