8OR7

Structure of a far-red induced allophycocyanin from Chroococcidiopsis thermalis sp. PCC 7203

8OR7 の概要

• エントリーDOI: 10.2210/pdb8or7/pdb
• 分子名称: Allophycocyanin beta subunit apoprotein, Phycocyanin, PHYCOCYANOBILIN, ... (6 entities in total)
• 機能のキーワード: photosynthesis, phycobiliprotein, allophycocyanin, far-red light photoacclimation
• 由来する生物種: Chroococcidiopsis thermalis; 詳細
• タンパク質・核酸の鎖数: 4
• 化学式量合計: 76254.65

構造登録者

Zhou, L.J.,Hoeppner, A.,Wang, Y.Q.,Zhao, K.H. (登録日: 2023-04-13, 公開日: 2024-03-20, 最終更新日: 2024-12-11)

主引用文献

Zhou, L.J.,Hoppner, A.,Wang, Y.Q.,Hou, J.Y.,Scheer, H.,Zhao, K.H.
Crystallographic and biochemical analyses of a far-red allophycocyanin to address the mechanism of the super-red-shift.
Photosynth.Res., 162:171-185, 2024

PubMed Abstract: Far-red absorbing allophycocyanins (APC), identified in cyanobacteria capable of FRL photoacclimation (FaRLiP) and low-light photoacclimation (LoLiP), absorb far-red light, functioning in energy transfer as light-harvesting proteins. We report an optimized method to obtain high purity far-red absorbing allophycocyanin B, AP-B2, of Chroococcidiopsis thermalis sp. PCC7203 by synthesis in Escherichia coli and an improved purification protocol. The crystal structure of the trimer, (PCB-ApcD5/PCB-ApcB2), has been resolved to 2.8 Å. The main difference to conventional APCs absorbing in the 650-670 nm range is a largely flat chromophore with the co-planarity extending, in particular, from rings BCD to ring A. This effectively extends the conjugation system of PCB and contributes to the super-red-shifted absorption of the α-subunit (λ = 697 nm). On complexation with the β-subunit, it is even further red-shifted (λ = 707 nm, λ = 721 nm). The relevance of ring A for this shift is supported by mutagenesis data. A variant of the α-subunit, I123M, has been generated that shows an intense FR-band already in the absence of the β-subunit, a possible model is discussed. Two additional mechanisms are known to red-shift the chromophore spectrum: lactam-lactim tautomerism and deprotonation of the chromophore that both mechanisms appear inconsistent with our data, leaving this question unresolved.

PubMed: 38182842
DOI: 10.1007/s11120-023-01066-2

実験手法

X-RAY DIFFRACTION (2.8 Å)