ジャーナル: J Mol Biol / 年: 2008 タイトル: Location and flexibility of the unique C-terminal tail of Aquifex aeolicus co-chaperonin protein 10 as derived by cryo-electron microscopy and biophysical techniques. 著者: Dong-Hua Chen / Kathryn Luke / Junjie Zhang / Wah Chiu / Pernilla Wittung-Stafshede / 要旨: Co-chaperonin protein 10 (cpn10, GroES in Escherichia coli) is a ring-shaped heptameric protein that facilitates substrate folding when in complex with cpn60 (GroEL in E. coli). The cpn10 from the ...Co-chaperonin protein 10 (cpn10, GroES in Escherichia coli) is a ring-shaped heptameric protein that facilitates substrate folding when in complex with cpn60 (GroEL in E. coli). The cpn10 from the hyperthermophilic, ancient bacterium Aquifex aeolicus (Aacpn10) has a 25-residue C-terminal extension in each monomer not found in any other cpn10 protein. Earlier in vitro work has shown that this tail is not needed for heptamer assembly or protein function. Without the tail, however, the heptamers (Aacpn10del-25) readily aggregate into fibrillar stacked rings. To explain this phenomenon, we performed binding experiments with a peptide construct of the tail to establish its specificity for Aacpn10del-25 and used cryo-electron microscopy to determine the three-dimensional (3D) structure of the GroEL-Aacpn10-ADP complex at an 8-A resolution. We found that the GroEL-Aacpn10 structure is similar to the GroEL-GroES structure at this resolution, suggesting that Aacpn10 has molecular interactions with cpn60 similar to other cpn10s. The cryo-electron microscopy density map does not directly reveal the density of the Aacpn10 25-residue tail. However, the 3D statistical variance coefficient map computed from multiple 3D reconstructions with randomly selected particle images suggests that the tail is located at the Aacpn10 monomer-monomer interface and extends toward the cis-ring apical domain of GroEL. The tail at this location does not block the formation of a functional co-chaperonin/chaperonin complex but limits self-aggregation into linear fibrils at high temperatures. In addition, the 3D variance coefficient map identifies several regions inside the GroEL-Aacpn10 complex that have flexible conformations. This observation is in full agreement with the structural properties of an effective chaperonin.
全体 : Aacpn10 capped to one end of GroEL under Mg-ADP
全体
名称: Aacpn10 capped to one end of GroEL under Mg-ADP
要素
試料: Aacpn10 capped to one end of GroEL under Mg-ADP
タンパク質・ペプチド: Chaperonin
タンパク質・ペプチド: Aquifex aeolicus co-chaperonin 10
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超分子 #1000: Aacpn10 capped to one end of GroEL under Mg-ADP
超分子
名称: Aacpn10 capped to one end of GroEL under Mg-ADP / タイプ: sample / ID: 1000 詳細: Aacpn10 was incubated with GroEL in 50 mM Tris-HCl, 30 mM MgCl2, 2 mM ADP, pH 7.5 at 37 Celsius for 1 hour 集合状態: One heptamer of Aacpn10 and seven ADP bind to one heptamer of GroEL Number unique components: 2
タイプ: NEGATIVE 詳細: The sample solution was blotted for 2.5 s before submersion in liquid ethane cooled by liquid nitrogen using FEI Vitrobot
グリッド
詳細: 400 mesh copper grid (R1.2/1.3 Quantifoil)
凍結
凍結剤: ETHANE / チャンバー内湿度: 95 % / チャンバー内温度: 4.2 K / 装置: OTHER / 詳細: Vitrification instrument: Vitrobot / 手法: blot for 2.5 s before plunging
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電子顕微鏡法
顕微鏡
JEOL 3000SFF
温度
最低: 4.2 K / 最高: 4.2 K / 平均: 4.2 K
アライメント法
Legacy - 非点収差: objective lens astigmatism was corrected at 400,000 times magnification
詳細
Yoshi MDS box for low-dose imaging
日付
2007年2月16日
撮影
カテゴリ: FILM / フィルム・検出器のモデル: KODAK SO-163 FILM デジタル化 - スキャナー: NIKON SUPER COOLSCAN 9000 デジタル化 - サンプリング間隔: 6.35 µm / 実像数: 720 / 平均電子線量: 36 e/Å2 詳細: The particle images were averaged by 2 to give 1.91 Angstrom per pixel. The final corrected pixel size for the 3D density map is 1.8 Angstrom per pixel. ビット/ピクセル: 8
The ratio of GroEL monomers to Aacpn10 monomers was about 1
CTF補正
詳細: each micrograph
最終 再構成
想定した対称性 - 点群: C7 (7回回転対称) / アルゴリズム: OTHER / 解像度のタイプ: BY AUTHOR / 解像度: 8.0 Å / 解像度の算出法: FSC 0.5 CUT-OFF / ソフトウェア - 名称: EMAN 詳細: The final map was calculated from the class averages and was filtered to show the subnanometer resolution features. 使用した粒子像数: 10772
PDBEntryID_givenInChain. Protocol: domain-based rigid body. UROX was used to perform the domain-as-rigid-body fitting of the GroEL-GroES-ADP crystal structure into the cryo-EM density map of the GroEL-Aacpn10-ADP complex
精密化
空間: REAL / プロトコル: RIGID BODY FIT / 当てはまり具合の基準: cross correlation