In Cubo Crystallization of Membrane Proteins

Abstract

One of the best options to understand the structures and hence functions of membrane proteins is macromolecular crystallography which demands for their three-dimensional (3D) crystals. The current chapter is focused on the lipid bicontinuous cubic phase method which is known to produce such crystals and is also called in cubo method. The lipid cubic phases are 3D self-assemblies consisting of two apposing aqueous regions separated by a lipid bilayer draped onto mathematical minimal surfaces. The dimensions of these phases lie in 6–25 nm range which act as an in vitro matrix for stabilization of membrane proteins from which they are crystallized for determining high resolution structures. The pros and cons of the in cubo method are presented with regard to other crystallization methods and also other lipid mesophases. Recent technological and methodological advances in addition to mechanistic principles are also discussed. The method is further explored for its advantages and potential cautions while going for its optimization and generalization. A brief survey of databases is also presented which may help for ready referral while using the in cubo method.