Crystals of sarcoplasmic reticulum Ca2+-ATPase

High-resolution structures of the Ca2+-ATPase have over the last 5 years added a structural dimension to our understanding of the function of this integral membrane protein. The Ca2+-ATPase is now by far the membrane protein where the most functionally different conformations have been described in precise structural detail. Here, we review our experience from solving Ca2+-ATPase structures: a purification scheme involving minimum handling of the protein to preserve natural and essential lipids, a rational approach to screening for crystals based on a limited number of polyethyleneglycols and many different salts, improving crystal quality using additives, collecting the data and finally solving the structures. We argue that certain of the lessons learned in the present study are very likely to be useful for crystallisation of eukaryotic membrane proteins in general.