Detergents as Tools in Membrane Biochemistry

Amphipols are a new class of surfactants that make it possible to handle membrane proteins in detergent-free aqueous solution as though they were soluble proteins. The strongly hydrophilic backbone of these polymers is grafted with hydrophobic chains, making them amphiphilic. Amphipols are able to stabilize in aqueous solution under their native state four well-characterized integral membrane proteins: (i) bacteriorhodopsin, (ii) a bacterial photosynthetic reaction center, (iii) cytochrome b6f, and (iv) matrix porin.

https://www.pnas.org/content/pnas/93/26/15047.full.pdf

Amphipols: Polymers that keep membrane proteins soluble in aqueous solutions

Membrane protein crystallization.

Models for the structure of outer-membrane proteins of Escherichia coli derived from Raman spectroscopy and prediction methods

Crystal structure of osmoporin OmpC from E. coli at 2.0 A

Publisher Summary This chapter describes isolation and crystallization of bacterial porin The unusual aspects of porin crystallization are consistent with the micellar interactions involved in crystal formation The resulting porin crystals are relatively sensitive to the environment Care must be taken in handling and mounting crystals for X-ray analysis to avoid significant or abrupt changes in the solvent or detergent environment and uncontrolled variations of temperature Porin has proven to be rather useful for the optimization of conditions to crystallize membrane proteins as it is very stable over a wide range of conditions Crystallization experiments (at 20°) are successful also using several other detergents with a moderate to high carboxymethyl cellulose (CMC) Initial problems with reproducibility of porin crystallization revealed that a high degree of purity of this protein is required, and that the removal of tightly bound lipoprotein and glycolipid is critical for success Although current experience is limited, it seems fair to conclude that with a better understanding of protein–amphiphile interactions, of micellar physical chemistry, and with improvement in crystallization techniques, the outlook for understanding membrane protein structure appears bright

J P Rosenbusch

Papers

Isolation and crystallization of bacterial porin.