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

International Tables for Crystallography (2012). Vol. F, ch. 4.2, p. 126   | 1 | 2 |

Section 4.2.6. Membrane-protein crystallization using cubic bicontinuous lipidic phases

H. Michela*

aMax-Planck-Institut für Biophysik, Heinrich-Hoffmann-Strasse 7, D-60528 Frankfurt/Main, Germany
Correspondence e-mail: michel@mpibp-frankfurt.mpg.de

4.2.6. Membrane-protein crystallization using cubic bicontinuous lipidic phases

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Landau & Rosenbusch (1996[link]) introduced the use of bicontinuous cubic phases of lipids for membrane-protein crystallization. In such phases, the lipid forms a single, curved, continuous three-dimensional bilayer [see Lindblom & Rilfors (1989[link]) for a review]. One can incorporate membrane proteins into such a bilayer, as demonstrated with octyl-β-D-glucopyranoside-solubilized monomeric bacteriorhodopsin. The three-dimensional bilayer network serves as a matrix for crystallization. The membrane protein can diffuse through the bilayer, but is also able to establish polar contacts in the third dimension. Landau & Rosenbusch demonstrated that bacteriorhodopsin forms small, well ordered three-dimensional crystals. The X-ray data indicate that the same two-dimensional crystals are present as formed by bacteriorhodopsin in its native environment (the purple membrane). These membranes are now stacked in the third dimension in a well ordered manner. Therefore, these crystals belong to type I.

The method has the conceptual problem that the growing three-dimensional crystal has to disrupt and displace the cubic lipidic phase. Nevertheless, it is hoped that this method can also be used for membrane proteins that do not have a strong tendency to form two-dimensional crystals spontaneously. In particular, this method appears to be the only chance for crystallizing those membrane proteins that are unstable in the absence of added lipids.

References

Landau, E. M. & Rosenbusch, J. P. (1996). Lipidic cubic phases: a novel concept for the crystallization of membrane proteins. Proc. Natl Acad. Sci. USA, 93, 14532–14535.
Lindblom, G. & Rilfors, L. (1989). Cubic phases and isotropic structures formed by membrane lipids – possible biological relevance. Biochim. Biophys. Acta, 988, 221–256.








































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