High-resolution cryoelectron microscopy

Henderson et al. [223] presented a detailed pattern of the structure of bacteriorhodopsin using high-resolution cryoelectron microscopy. Using X-ray and neutron diffraction techniques, Dencher et al. [224—227] could decode the... 

Henderson et al. [223] presented a detailed pattern of the structure of bacteriorhodopsin using high-resolution cryoelectron microscopy. Using X-ray and neutron diffraction techniques, Dencher et al. [224—227] could decode the secondary and tertiary structure of bacteriorhodopsin during the photocycle. Nevertheless, we should emphasize that the resolution still shows transitions in the active site (protonation of counterions, deprotonation of Schiff base, and reprotonation of counterions), leading to a metastable state of the protein. 

A detailed view of the kinesin-microtubule complex has been obtained by combining high-resolution structures of the individual components from X-ray crystallography (kinesin) and electron diffraction (tubulin Lowe et al., 2001 Nogales et al, 1998) with low-resolution models of kinesin-decorated microtubules obtained by cryoelectron microscopy and image reconstruction (Hirose et al, 1999 Hoenger et al., 2000 Kikkawa et al, 2001 Kozielski et al., 1998 Rice et al., 1999 Skiniotis et al., 2003 Wendt... 

The first structural location of the taxane binding site [42] placed it in the interprotofilament space, thus supporting the biochemical results. However, this changed when the first high resolution 3D structure of the paclitaxel-tubulin complex was solved by electron-crystallography of a two-dimensional zinc-induced tubulin polymer [5]. The fitting of this structure into a three-dimensional reconstruction of microtubules from cryoelectron microscopy allowed a pseudo atomic resolution model of microtubules [43] in which the paclitaxel binding site was placed inside the lumen of the microtubules hidden from the outer solvent. 

Detailed structural data are only available for a few highly selective charmels. The best characterized is the model system gramicidin, which has been elucidated using NMR-based techniques [14,15]. Among physiological systems, atomic level resolution structures (based on x-ray or cryoelectron microscopy) are available for a potassium channel from S. lividans (KcsA) [5], two prokargotic chloride channels [16], a stretch activated channel from M. tuberculosis [17], human red cell aquaporin-1 [18], and a glycerol facilitator from... 

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