Existing and emergent roles for surfactants in the three-dimensional crystallization of integral membrane proteins

The determination of protein structures by X-ray crystallography necessitat es the formation of well-ordered three-dimensional crystals that are grown from protein solutions. For integral membrane proteins, the protein solute consists of a protein surrounded by surfactant molecules; therefore, utiliz ation of surfactant properties to improve the probability of membrane prote in crystallization may provide the basis of rational crystallization method s. Properties of surfactants that may be germane to membrane protein crysta llization include consolute boundaries, the second virial coefficient B-22, and critical phenomena. Also, the non-lamellar lipidic cubic phase (LCP) h as been shown to be a unique matrix in which to form membrane protein cryst als. These physical and physical-chemical descriptors of surfactants (or li pids) are discussed in the context of relevance or potential relevance to t hree-dimensional membrane protein crystallization. Other topics covered inc lude the development of crystallization screens based upon surfactant prope rties, novel surfactants, and the use of additives to improve crystal quali ty. (C) 2001 Elsevier Science Ltd. All rights reserved.