National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
AI034036
米国
引用
ジャーナル: Nat Commun / 年: 2021 タイトル: Cryo-EM structure of cortical microtubules from human parasite Toxoplasma gondii identifies their microtubule inner proteins. 著者: Xiangli Wang / Yong Fu / Wandy L Beatty / Meisheng Ma / Alan Brown / L David Sibley / Rui Zhang / 要旨: In living cells, microtubules (MTs) play pleiotropic roles, which require very different mechanical properties. Unlike the dynamic MTs found in the cytoplasm of metazoan cells, the specialized ...In living cells, microtubules (MTs) play pleiotropic roles, which require very different mechanical properties. Unlike the dynamic MTs found in the cytoplasm of metazoan cells, the specialized cortical MTs from Toxoplasma gondii, a prevalent human pathogen, are extraordinarily stable and resistant to detergent and cold treatments. Using single-particle cryo-EM, we determine their ex vivo structure and identify three proteins (TrxL1, TrxL2 and SPM1) as bona fide microtubule inner proteins (MIPs). These three MIPs form a mesh on the luminal surface and simultaneously stabilize the tubulin lattice in both longitudinal and lateral directions. Consistent with previous observations, deletion of the identified MIPs compromises MT stability and integrity under challenges by chemical treatments. We also visualize a small molecule like density at the Taxol-binding site of β-tubulin. Our results provide the structural basis to understand the stability of cortical MTs and suggest an evolutionarily conserved mechanism of MT stabilization from the inside.
選択した数: 536132 詳細: Cortical MTs were manually picked from the motion-corrected micrographs using the APPION image-processing suite. The selected MT segments were computationally cut into overlapping boxes ...詳細: Cortical MTs were manually picked from the motion-corrected micrographs using the APPION image-processing suite. The selected MT segments were computationally cut into overlapping boxes (512x512 pixels) with an 8-nm non-overlapping region (step size) between adjacent boxes (corresponding to the length of a tubulin heterodimer). We refer to these boxed images as 8-nm MT particles.
CTF補正
ソフトウェア: (名称: Gctf (ver. 1.18), RELION (ver. 3.1), cryoSPARC (ver. 2.15)) 詳細: CTF amplitude correction was performed as part of the 3D reconstruction.
初期モデル
モデルのタイプ: EMDB MAP 詳細: We used 13- and 14-protofilament bovine GMPCPP-MTs as the initial models, and performed multi-reference sorting of all the 8-nm MT particles using EMAN1.
タイプ: PROJECTION MATCHING Projection matching processing - Number reference projections: 300 Projection matching processing - Angular sampling: 3.0 degrees ソフトウェア - 名称: EMAN (ver. 1.9) 詳細: The classification result indicated that T. Gondii cortical MTs are exclusively 13-protofilament MTs.
最終 角度割当
タイプ: MAXIMUM LIKELIHOOD / ソフトウェア - 名称: RELION (ver. 3.1) 詳細: Next, we performed single-reference refinement using Refine3D in RELION-3 software with global search of alignment parameters. The structure gradually converged to a 13-protofilament MT with ...詳細: Next, we performed single-reference refinement using Refine3D in RELION-3 software with global search of alignment parameters. The structure gradually converged to a 13-protofilament MT with 3-start helix and only one seam.
最終 3次元分類
クラス数: 2 / ソフトウェア - 名称: RELION (ver. 3.1) 詳細: To separate the particles with and without TrxL2, we signal-subtracted the tubulin densities from the raw particle images using Particle subtraction in RELION-3, and then performed 3D ...詳細: To separate the particles with and without TrxL2, we signal-subtracted the tubulin densities from the raw particle images using Particle subtraction in RELION-3, and then performed 3D classification with a soft-edged cylindrical mask covering only the TrxL2 densities at either site x or y. For each site, the 3D classification was able to produce two clean classes, corresponding to the bound and unbound states of TrxL2.
Secondary structure, Ramachandran, and rotamer restraints were applied during refinement. The nonbonded_weight value was set to 500 to reduce the clashes between atoms.