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Technology Topics Crystallography

A new amphiphile for crystallizing membrane proteins

SBKB [doi:10.1038/sbkb.2010.58]
Technical Highlight - January 2011
Short description: An easy-to-use chemical approach for stabilizing, extracting and crystallizing integral membrane proteins.

X-ray diffraction by a cytochrome bf crystal obtained in the presence of MNG-3.

Membrane proteins are very difficult to work with. Generally, a detergent is used to solubilize these proteins, but it is not always possible to find a suitable one because many membrane proteins denature or aggregate even in the presence of detergent.

Several attempts to develop alternative ways of solubilizing such proteins have been tried, and perhaps nanodiscs are the most promising. But there is still a need for amphiphiles that can extract proteins from the membrane and be suitable for crystallization studies.

Samuel Gellman and his team, in collaboration with PSI CESG, have synthesized a new class of amphiphile, which they term maltose-neopentyl glycol (MNG) amphiphiles. The design features a quaternary carbon atom that is derived from neopentyl glycol, chosen because the quaternary nature of the carbon will reduce conformational flexibility. Hydrophilic groups from maltose were then added, producing a molecule with two hydrophilic and two lipophilic subunits.

When tested with several different membrane proteins, MNG amphiphiles work better than conventional detergents for stabilizing and extracting integral membrane proteins. Native folding, association and function are maintained, and an MNG aids the crystallization of cytochrome b6f complex from Chlamydomonas reinhardtii. The diffraction data extended to 3.4-Å resolution.

Results also indicate that MNG is compatible with lipid cubic phase (LCP) membrane protein crystallization.

Many MNGs can be easily synthesized in gram quantities and can be adapted for other membrane proteins. This looks like a promising way to tackle integral membrane protein structures.

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References

  1. P.S. Chae et al. Maltose–neopentyl glyco (MNG) amphiphiles for solubilisation, stabilization and crystallization of membrane proteins.
    Nat. Meth. 7, 1003-1008 (2010). doi:10.138/nmeth.1526

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