ジャーナル: J Struct Biol / 年: 2001 タイトル: Lumbricus terrestris hemoglobin--the architecture of linker chains and structural variation of the central toroid. 著者: F Mouche / N Boisset / P A Penczek / 要旨: The extracellular giant hemoglobin from the earthworm Lumbricus terrestris was reconstructed at 14.9-A resolution from cryo-electron microscope images, using a new procedure for estimating parameters ...The extracellular giant hemoglobin from the earthworm Lumbricus terrestris was reconstructed at 14.9-A resolution from cryo-electron microscope images, using a new procedure for estimating parameters of the contrast transfer (CTF) function. In this approach, two important CTF parameters, defocus and amplitude contrast ratio, can be refined iteratively within the framework of 3D projection alignment procedure, using minimization of sign disagreement between theoretical CTF and cross-resolution curves. The 3D cryo-EM map is in overall good agreement with the recent X-ray crystallography map of Royer et al. (2000, Proc. Natl. Acad. Sci. USA 97, 7107-7111), and it reveals the local threefold arrangement of the three linker chains present within each 1/12 of the complex. The 144 globin chains and 36 linker chains within the complex are clearly visible, and the interdigitation of the 12 coiled-coil helical spokes forming the central toroidal piece is confirmed. Based on these findings, two mechanisms of the dodecameric unit assembly are proposed and termed "zigzag" and "pairwise" polymerizations. However, the detection by cryo-EM of 12 additional rod-like bodies within the toroid raises the possibility that the architecture of the toroid is more complex than previously thought or that yet unknown ligands or allosteric effectors for this oxygen carrier are present.
Images recorded at 200 kV with a magnification of x60000 on a Jeol JEM2010F. Condensor aperture 150 um. Objective aperture 60 um. Defocus within a range of 1.3 to 3.2 um.
CTF補正
詳細: Wiener filtering on volumes
最終 再構成
想定した対称性 - 点群: D6 (2回x6回 2面回転対称) アルゴリズム: OTHER / 解像度のタイプ: BY AUTHOR / 解像度: 14.9 Å / 解像度の算出法: FSC 0.5 CUT-OFF / ソフトウェア - 名称: SPIDER / 詳細: SIRT on single 2D-projections / 使用した粒子像数: 7770