当前位置: X-MOL 学术Photosynth. Res. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
The structural basis of far-red light absorbance by allophycocyanins
Photosynthesis Research ( IF 3.7 ) Pub Date : 2020-10-14 , DOI: 10.1007/s11120-020-00787-y
Nathan Soulier 1 , Donald A Bryant 1, 2, 3
Affiliation  

Phycobilisomes (PBS), the major light-harvesting antenna in cyanobacteria, are supramolecular complexes of colorless linkers and heterodimeric, pigment-binding phycobiliproteins. Phycocyanin and phycoerythrin commonly comprise peripheral rods, and a multi-cylindrical core is principally assembled from allophycocyanin (AP). Each AP subunit binds one phycocyanobilin (PCB) chromophore, a linear tetrapyrrole that predominantly absorbs in the orange-red region of the visible spectrum (600–700 nm). AP facilitates excitation energy transfer from PBS peripheral rods or from directly absorbed red light to accessory chlorophylls in the photosystems. Paralogous forms of AP that bind PCB and are capable of absorbing far-red light (FRL; 700–800 nm) have recently been identified in organisms performing two types of photoacclimation: FRL photoacclimation (FaRLiP) and low-light photoacclimation (LoLiP). The FRL-absorbing AP (FRL-AP) from the thermophilic LoLiP strain Synechococcus sp. A1463 was chosen as a platform for site-specific mutagenesis to probe the structural differences between APs that absorb in the visible region and FRL-APs and to identify residues essential for the FRL absorbance phenotype. Conversely, red light-absorbing allophycocyanin-B (AP-B; ~ 670 nm) from the same organism was used as a platform for creating a FRL-AP. We demonstrate that the protein environment immediately surrounding pyrrole ring A of PCB on the alpha subunit is mostly responsible for the FRL absorbance of FRL-APs. We also show that interactions between PCBs bound to alpha and beta subunits of adjacent protomers in trimeric AP complexes are responsible for a large bathochromic shift of about ~ 20 nm and notable sharpening of the long-wavelength absorbance band.



中文翻译:

别藻蓝蛋白吸收远红光的结构基础

藻胆体 (PBS) 是蓝藻中主要的捕光天线,是无色接头和异二聚体、色素结合藻胆蛋白的超分子复合物。藻蓝蛋白和藻红蛋白通常包含外围杆,多圆柱核主要由别藻蓝蛋白 (AP) 组装而成。每个 AP 亚基结合一个藻蓝蛋白 (PCB) 发色团,这是一种线性四吡咯,主要在可见光谱(600-700 nm)的橙红色区域吸收。AP 促进从 PBS 外围杆或从直接吸收的红光到光系统中的辅助叶绿素的激发能量转移。最近在执行两种光驯化的生物体中发现了与 PCB 结合并能够吸收远红光(FRL;700-800 nm)的 AP 的旁系同源形式:FRL 光驯化 (FaRLiP) 和低光光驯化 (LoLiP)。来自嗜热 LoLiP 菌株的 FRL 吸收 AP (FRL-AP)聚球藻属 A1463 被选作位点特异性诱变的平台,以探测在可见光区吸收的 AP 与 FRL-AP 之间的结构差异,并确定 FRL 吸收表型所必需的残基。相反,来自同一生物体的吸收红光的别藻蓝蛋白-B(AP-B;~670 nm)被用作创建 FRL-AP 的平台。我们证明了紧邻 alpha 亚基上 PCB 吡咯环 A 的蛋白质环境主要负责 FRL-APs 的 FRL 吸光度。我们还表明,三聚体 AP 复合物中与相邻原体的 alpha 和 beta 亚基结合的 PCB 之间的相互作用导致了大约 20 nm 的大红移和长波长吸收带的显着锐化。

更新日期:2020-10-14
down
wechat
bug