Membrane proteins are embedded in the cell membrane bilayer, serving as gatekeepers, enabling signals, solutes, and other important cellular currency to traverse the otherwise insoluble bilayer. Some act like channels or sensors. Others, like the BR ion pump, either passively or actively transport nutrients and other biochemicals. Scientists know the structure of about 30 membrane proteins, explains Luecke, even though one-quarter of most genomes code for them. "There are many more protein membranes than people like to think." These proteins are very unstable and don't readily crystallize, making it difficult to collect the kind of x-ray data commonly used to study protein structure.
But developments in high-resolution x-ray crystallography have given scientists a sophisticated new tool, cubic lipid phase (CLP) crystallization,1 which serves as a "whole new way to coerce membrane proteins to crystallize," Luecke says. He and his colleagues used this technique to achieve the results described in this ...
