Biophysical Journal Volume 110 February 2016 E01
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Editorial Biophysical Journal Special Issue: Focus on Cryo-EM In structural biology, x-ray diffraction was first used to solve the structure of proteins (1) and nucleic acids (2). Nuclear magnetic resonance spectroscopy emerged much later as an alternate approach that allows atomic models of macromolecules to be built from solution studies (3). A third approach, cryo-electron microscopy (cryo-EM), may become the dominant method for structure determination of large macromolecular complexes. As many are aware, there has been a recent revolution in the field of cryo-EM, mainly driven by the introduction of new direct electron detectors (4,5). It has now become possible to fairly rapidly achieve a near-atomic level of resolution for many macromolecular complexes. As Venki Ramakrishnan recently wrote (6): ‘‘It is safe to predict that for large complexes, cryo-EM will largely supersede crystallography.’’ This is a strong statement from someone who shared the Nobel Prize for his crystallographic studies of the ribosome! We therefore thought that the time was ripe for a Special Focus issue of Biophysical Journal devoted to cryo-EM. This issue covers a broad range of topics in cryo-EM, starting with a personal reminiscence by Jacques Dubochet about the origins of vitrification of samples. What has now become clear from many high-resolution cryo-EM studies is that this rather simple approach developed by Dubochet and colleagues (7) allows for the complete preservation of structures in a fully hydrated and cryo-fixed state so that they may be imaged in the vacuum of an electron microscope. ˚ resolution cryo-EM A recent paper presenting a 2.2 A reconstruction of a protein complex (8) suggests that the limitation in resolution in cryo-EM may actually be the
intrinsic flexibility of macromolecules when in solution and not packed in a crystal. Because no one could have predicted three years ago where the field of cryo-EM would be today, we will not attempt to speculate about how the field will progress over the next few years. But we can expect that progress will continue to be rapid, and that the impact of such biophysical studies on our understanding of life, health, and disease will be great. Edward H. Egelman,1,* and Andreas Engel2 University of Virginia, Charlottesville, Virgina; and 2 Delft University of Technology, Delft, the Netherlands
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REFERENCES 1. Kendrew, J. C., and M. F. Perutz. 1957. X-ray studies of compounds of biological interest. Annu. Rev. Biochem. 26:327–372. 2. Watson, J. D., and F. H. Crick. 1953. Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid. Nature. 171:737–738. 3. Wu¨thrich, K. 2001. The way to NMR structures of proteins. Nat. Struct. Biol. 8:923–925. 4. Ku¨hlbrandt, W. 2014. Cryo-EM enters a new era. eLife. 3:e03678. 5. Egelman, E. H. 2016. The current revolution in cryo-EM. Biophys. J. 110, in press. 6. Ramakrishnan, V. 2014. The ribosome emerges from a black box. Cell. 159:979–984. 7. Dubochet, J., M. Adrian, ., P. Schultz. 1988. Cryo-electron microscopy of vitrified specimens. Q.Rev.Biophys. 21:129–228. ˚ resolution 8. Bartesaghi, A., A. Merk, ., S. Subramaniam. 2015. 2.2 A cryo-EM structure of b-galactosidase in complex with a cell-permeant inhibitor. Science. 348:1147–1151.
Submitted January 25, 2016, and accepted for publication January 25, 2016. *Correspondence: [email protected] Ó 2016 by the Biophysical Society 0006-3495/16/02/0001/1
http://dx.doi.org/10.1016/j.bpj.2016.01.025
E01
Editorial Biophysical Journal Special Issue: Focus on Cryo-EM In structural biology, x-ray diffraction was first used to solve the structure of proteins (1) and nucleic acids (2). Nuclear magnetic resonance spectroscopy emerged much later as an alternate approach that allows atomic models of macromolecules to be built from solution studies (3). A third approach, cryo-electron microscopy (cryo-EM), may become the dominant method for structure determination of large macromolecular complexes. As many are aware, there has been a recent revolution in the field of cryo-EM, mainly driven by the introduction of new direct electron detectors (4,5). It has now become possible to fairly rapidly achieve a near-atomic level of resolution for many macromolecular complexes. As Venki Ramakrishnan recently wrote (6): ‘‘It is safe to predict that for large complexes, cryo-EM will largely supersede crystallography.’’ This is a strong statement from someone who shared the Nobel Prize for his crystallographic studies of the ribosome! We therefore thought that the time was ripe for a Special Focus issue of Biophysical Journal devoted to cryo-EM. This issue covers a broad range of topics in cryo-EM, starting with a personal reminiscence by Jacques Dubochet about the origins of vitrification of samples. What has now become clear from many high-resolution cryo-EM studies is that this rather simple approach developed by Dubochet and colleagues (7) allows for the complete preservation of structures in a fully hydrated and cryo-fixed state so that they may be imaged in the vacuum of an electron microscope. ˚ resolution cryo-EM A recent paper presenting a 2.2 A reconstruction of a protein complex (8) suggests that the limitation in resolution in cryo-EM may actually be the
intrinsic flexibility of macromolecules when in solution and not packed in a crystal. Because no one could have predicted three years ago where the field of cryo-EM would be today, we will not attempt to speculate about how the field will progress over the next few years. But we can expect that progress will continue to be rapid, and that the impact of such biophysical studies on our understanding of life, health, and disease will be great. Edward H. Egelman,1,* and Andreas Engel2 University of Virginia, Charlottesville, Virgina; and 2 Delft University of Technology, Delft, the Netherlands
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REFERENCES 1. Kendrew, J. C., and M. F. Perutz. 1957. X-ray studies of compounds of biological interest. Annu. Rev. Biochem. 26:327–372. 2. Watson, J. D., and F. H. Crick. 1953. Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid. Nature. 171:737–738. 3. Wu¨thrich, K. 2001. The way to NMR structures of proteins. Nat. Struct. Biol. 8:923–925. 4. Ku¨hlbrandt, W. 2014. Cryo-EM enters a new era. eLife. 3:e03678. 5. Egelman, E. H. 2016. The current revolution in cryo-EM. Biophys. J. 110, in press. 6. Ramakrishnan, V. 2014. The ribosome emerges from a black box. Cell. 159:979–984. 7. Dubochet, J., M. Adrian, ., P. Schultz. 1988. Cryo-electron microscopy of vitrified specimens. Q.Rev.Biophys. 21:129–228. ˚ resolution 8. Bartesaghi, A., A. Merk, ., S. Subramaniam. 2015. 2.2 A cryo-EM structure of b-galactosidase in complex with a cell-permeant inhibitor. Science. 348:1147–1151.
Submitted January 25, 2016, and accepted for publication January 25, 2016. *Correspondence: [email protected] Ó 2016 by the Biophysical Society 0006-3495/16/02/0001/1
http://dx.doi.org/10.1016/j.bpj.2016.01.025
