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基本情報
登録情報 | データベース: PDB / ID: 3jbb | ||||||
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タイトル | Characterization of red-shifted phycobiliprotein complexes isolated from the chlorophyll f-containing cyanobacterium Halomicronema hongdechloris | ||||||
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![]() | PHOTOSYNTHESIS / alpha-helical phycobiliprotein / light harvesting / phycocyano methylation on ASN71 in APCB SUBUNIT / phycobilisome | ||||||
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手法 | 電子顕微鏡法 / 単粒子再構成法 / ネガティブ染色法 / 解像度: 26 Å | ||||||
![]() | Li, Y. / Lin, Y. / Garvey, C. / Birch, D. / Corkery, R.W. / Loughlin, P.C. / Scheer, H. / Willows, R.D. / Chen, M. | ||||||
![]() | ![]() タイトル: Characterization of red-shifted phycobilisomes isolated from the chlorophyll f-containing cyanobacterium Halomicronema hongdechloris. 著者: Yaqiong Li / Yuankui Lin / Christopher J Garvey / Debra Birch / Robert W Corkery / Patrick C Loughlin / Hugo Scheer / Robert D Willows / Min Chen / ![]() ![]() ![]() 要旨: Phycobilisomes are the main light-harvesting protein complexes in cyanobacteria and some algae. It is commonly accepted that these complexes only absorb green and orange light, complementing ...Phycobilisomes are the main light-harvesting protein complexes in cyanobacteria and some algae. It is commonly accepted that these complexes only absorb green and orange light, complementing chlorophyll absorbance. Here, we present a new phycobilisome derived complex that consists only of allophycocyanin core subunits, having red-shifted absorption peaks of 653 and 712 nm. These red-shifted phycobiliprotein complexes were isolated from the chlorophyll f-containing cyanobacterium, Halomicronema hongdechloris, grown under monochromatic 730 nm-wavelength (far-red) light. The 3D model obtained from single particle analysis reveals a double disk assembly of 120-145 Å with two α/β allophycocyanin trimers fitting into the two separated disks. They are significantly smaller than typical phycobilisomes formed from allophycocyanin subunits and core-membrane linker proteins, which fit well with a reduced distance between thylakoid membranes observed from cells grown under far-red light. Spectral analysis of the dissociated and denatured phycobiliprotein complexes grown under both these light conditions shows that the same bilin chromophore, phycocyanobilin, is exclusively used. Our findings show that red-shifted phycobilisomes are required for assisting efficient far-red light harvesting. Their discovery provides new insights into the molecular mechanisms of light harvesting under extreme conditions for photosynthesis, as well as the strategies involved in flexible chromatic acclimation to diverse light conditions. #1: ![]() タイトル: The structure of allophycocyanin B from Synechocystis PCC 6803 reveals the structural basis for the extreme redshift of the terminal emitter in phycobilisomes. 著者: Pan Pan Peng / Liang Liang Dong / Ya Fang Sun / Xiao Li Zeng / Wen Long Ding / Hugo Scheer / Xiaojing Yang / Kai Hong Zhao / ![]() ![]() ![]() 要旨: Allophycocyanin B (AP-B) is one of the two terminal emitters in phycobilisomes, the unique light-harvesting complexes of cyanobacteria and red algae. Its low excitation-energy level and the ...Allophycocyanin B (AP-B) is one of the two terminal emitters in phycobilisomes, the unique light-harvesting complexes of cyanobacteria and red algae. Its low excitation-energy level and the correspondingly redshifted absorption and fluorescence emission play an important role in funnelling excitation energy from the hundreds of chromophores of the extramembraneous phycobilisome to the reaction centres within the photosynthetic membrane. In the absence of crystal structures of these low-abundance terminal emitters, the molecular basis for the extreme redshift and directional energy transfer is largely unknown. Here, the crystal structure of trimeric AP-B [(ApcD/ApcB)3] from Synechocystis sp. PCC 6803 at 1.75 Å resolution is reported. In the crystal lattice, eight trimers of AP-B form a porous, spherical, 48-subunit assembly of 193 Å in diameter with an internal cavity of 1.1 × 10(6) Å(3). While the overall structure of trimeric AP-B is similar to those reported for many other phycobiliprotein trimers, the chromophore pocket of the α-subunit, ApcD, has more bulky residues that tightly pack the phycocyanobilin (PCB). Ring D of the chromophores is further stabilized by close interactions with ApcB from the adjacent monomer. The combined contributions from both subunits render the conjugated rings B, C and D of the PCB in ApcD almost perfectly coplanar. Together with mutagenesis data, it is proposed that the enhanced planarity effectively extends the conjugation system of PCB and leads to the redshifted absorption (λmax = 669 nm) and fluorescence emission (679 nm) of the ApcD chromophore in AP-B, thereby enabling highly efficient energy transfer from the phycobilisome core to the reaction centres. | ||||||
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-検証レポート
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-関連構造データ
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リンク
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集合体
登録構造単位 | ![]()
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要素
#1: タンパク質 | 分子量: 18769.273 Da / 分子数: 6 / 断片: APCD subunit (SEE REMARK 999) / 由来タイプ: 天然 由来: (天然) ![]() 参照: UniProt: A0A0R4I959*PLUS #2: タンパク質 | 分子量: 17245.629 Da / 分子数: 6 / 断片: APCB subunit (SEE REMARK 999) / 由来タイプ: 天然 由来: (天然) ![]() 参照: UniProt: A0A0R4I960*PLUS #3: 化合物 | ChemComp-CYC / #4: 化合物 | ChemComp-SO4 / #5: 水 | ChemComp-HOH / | Has protein modification | Y | 配列の詳細 | THE IMAGED PROTEINS ARE FROM HALOMICRONEMA HONGDECHLORIS, BUT THE MODELED SEQUENCES ARE FROM ...THE IMAGED PROTEINS ARE FROM HALOMICRON | |
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-実験情報
-実験
実験 | 手法: 電子顕微鏡法 / 使用した結晶の数: 1 |
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EM実験 | 試料の集合状態: PARTICLE / 3次元再構成法: 単粒子再構成法 |
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試料調製
構成要素 |
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緩衝液 | 名称: 0.8 M phosphate buffer / pH: 7.5 / 詳細: 0.8 M phosphate buffer | |||||||||||||||
試料 | 包埋: NO / シャドウイング: NO / 染色: YES / 凍結: NO / 詳細: 2% uranyl acetate for 2-3 seconds | |||||||||||||||
染色 | タイプ: NEGATIVE / 染色剤: uranyl acetate | |||||||||||||||
試料支持 | 詳細: 200 mesh gold grid with thin carbon support |
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電子顕微鏡撮影
顕微鏡 | モデル: FEI/PHILIPS CM10 / 日付: 2015年6月8日 / 詳細: PHILIPS CM10 |
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電子銃 | 電子線源: TUNGSTEN HAIRPIN / 加速電圧: 100 kV / 照射モード: FLOOD BEAM |
電子レンズ | モード: BRIGHT FIELD / 倍率(公称値): 180000 X / 最大 デフォーカス(公称値): 3000 nm |
試料ホルダ | 試料ホルダーモデル: PHILIPS ROTATION HOLDER |
撮影 | フィルム・検出器のモデル: GENERIC IMAGE PLATES |
画像スキャン | デジタル画像の数: 12 |
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解析
EMソフトウェア |
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CTF補正 | 詳細: Each particle | ||||||||||||
対称性 | 点対称性: D3 (2回x3回 2面回転対称) | ||||||||||||
3次元再構成 | 手法: Cross-common lines / 解像度: 26 Å / 解像度の算出法: FSC 0.33 CUT-OFF / 粒子像の数: 420 / ピクセルサイズ(公称値): 3.8 Å / ピクセルサイズ(実測値): 3.8 Å 詳細: (Single particle details: Semiautomatic selection using e2boxer.py swarm function) (Single particle--Applied symmetry: D3) クラス平均像の数: 32 / 対称性のタイプ: POINT | ||||||||||||
原子モデル構築 | プロトコル: RIGID BODY FIT / 空間: REAL 詳細: REFINEMENT PROTOCOL--rigid body DETAILS--Two trimers were fitted to each end of the EM map. 99.5% of atoms fit within the map at contour level 0.87 | ||||||||||||
原子モデル構築 | 3D fitting-ID: 1 / Accession code: 4PO5 / Initial refinement model-ID: 1 / PDB-ID: 4PO5 / Source name: PDB / タイプ: experimental model
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精密化ステップ | サイクル: LAST
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