Use of detergents in two-dimensional crystallization of membrane proteins

Structure determination at high resolution is actually a difficult challeng e for membrane proteins and the number of membrane proteins that have been crystallized is still small and far behind that of soluble proteins. Becaus e of their amphiphilic character, membrane proteins need to be isolated, pu rified and crystallized in detergent solutions. This makes it difficult to grow the well-ordered three-dimensional crystals that are required for high resolution structure analysis by X-ray crystallography. In this difficult context, growing crystals confined to two dimensions (2D crystals) and thei r structural analysis by electron crystallography has opened a new way to s olve the structure of membrane proteins. However, 2D crystallization is one of the major bottlenecks in the structural studies of membrane proteins. A dvances in our understanding of the interaction between proteins, lipids an d detergents as well as development and improvement of new strategies will facilitate the success rate of 2D crystallization. This review deals with t he various available strategies for obtaining 2D crystals from detergent-so lubilized intrinsic membrane proteins. It gives an overview of the methods that have been applied and gives details and suggestions of the physical pr ocesses leading to the formation of the ordered arrays which may be of help for getting more proteins crystallized in a form suitable for high resolut ion structural analysis by electron crystallography. (C) 2000 Elsevier Scie nce B.V. All rights reserved.