International
Tables for
Crystallography
Volume F
Crystallography of biological macromolecules
Edited by M. G. Rossmann and E. Arnold

International Tables for Crystallography (2006). Vol. F. ch. 19.2, p. 427   | 1 | 2 |

Section 19.2.4.3. 3D map

W. Chiua*

aVerna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
Correspondence e-mail: wah@bcm.tmc.edu

19.2.4.3. 3D map

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The three-dimensional (3D) map is computed from the amplitudes and phases at the resolution defined by the data (Henderson & Unwin, 1975[link]). The resolution reported for the structure is defined by the observed reflections in the images. Owing to the missing data at high tilt angles, the reconstruction normally has a lower resolution in the direction of the electron beam than in the direction normal to it. As a result, many of the initial low-resolution structures appear stretched out along the vertical direction. The interpretation of the 3D map derived from electron crystallography is similar to that of X-ray crystallography. Often, the initial map is reported at about 7 Å, where some of the α-helices can be interpreted. With an improved map of about 3.5 Å, the polypeptide backbone is traced and some of the bulky side chains are recognized. Fig. 19.2.4.3[link] shows a chain tracing of a tubulin crystal (Nogales et al., 1998[link]).

[Figure 19.2.4.3]

Figure 19.2.4.3| top | pdf |

Ribbon diagram of a tubulin dimer, whose structure has been solved to 3.7 Å resolution. GTP, GDP and taxol are shown as CPK models, with GDP at the top, bound to β tubulin, and GTP in the middle, bound to the α subunit. This is the view as seen from inside a microtubule, with the plus end at the top. (Courtesy of Drs Eva Nogales and Kenneth Downing at the Lawrence Berkeley National Laboratory, University of California, Berkeley.)

References

First citation Henderson, R. & Unwin, P. N. (1975). Three-dimensional model of purple membrane obtained by electron microscopy. Nature (London), 257, 28–32.Google Scholar
First citation Nogales, E., Wolf, S. G. & Downing, K. H. (1998). Structure of the alpha beta tubulin dimer by electron crystallography. Nature (London), 391, 199–203.Google Scholar








































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