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is reconstituted back to a lipid bilayer and then precipitant is added
directly to the lipid/protein phase to initiate membrane protein crystal-
lization. This approach will be considered in more detail in what
follows.
The most successful detergents for membrane protein solubilization
and crystallization are presented the Table 1. Lists presenting the deter-
gents that have been most efficiently used in structure determination are
available from several Internet sites that track the known 3D structures of
membrane proteins (for example:
http://blanco.biomol.uci.edu/Membrane_Proteins_xtal.html,
http://www.mpibp-frankfurt.mpg.de/michel/public/memprotstruct.html,
http://www.mpdb.ul.ie) (Prive, 2007).
In meso Membrane Protein Crystallization
Cubic phase crystallization
Recent success in the crystallization of membrane proteins in lipid cubic
phase systems has provided the hope for a breakthrough in the field.
Indeed, broad success has recently been achieved in using lipid bilayers to
crystallize the
Halobacterial
family of rhodopsins. Among these proteins
there is bacteriorhodopsin (Pebay-Peyroula
et al
., 1997), which, as men-
tioned, has been one of the most difficult membrane proteins to crystallize
in the detergent-soluble state.
Another example is the crystallization and elucidation of the structure
and functional mechanisms of the first complex of two membrane pro-
teins: sensory rhodopsin II and transducer II, which is mediating phototaxis
in
Natronobacterium pharaonis
(Gordeliy
et al
., 2002; Moukhametzianov
et al
., 2006). It is worth mentioning that the complex has monomeric con-
tent in the detergent-soluble state and the native dimeric state only in lipid
membranes. It is likely that the complex cannot be crystallized from deter-
gent solutions.
Very recent success in cubic phase crystallization leading to the first
high resolution structure of the first ligand binding GPCR, human
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