DESIGNED ADDITIVES FOR CONTROLLED GROWTH OF CRYSTALS OF PHOSPHOLIPID INTERACTING PROTEINS - SHORT-CHAIN PHOSPHOLIPIDS

A new approach to crystallization of proteins that interact with lipid s has been applied to the protein crambin. Short chain phospholipids a re water-soluble additives and effectively lower the amount of protein needed to form crambin crystals by lowering protein solubility and in hibiting crystal growth in the fastest growing direction. Compared wit h optimal crystallization conditions without phospholipid, which gave large crambin crystals (1.5 X 0.7 X 0.5 mm), a 30-60-fold decrease in protein concentration as well as 5-fold decrease in volume were achiev ed. As a result, the efficiency of crystal production was increased by 150-300-fold. The crystals obtained diffracted beyond 1.5 Angstrom re solution. The most effective additive, phosphotidylcholine, had a size comparable to the proposed binding site on crambin and on the homolog ous membrane-active toxins. The procedure developed may be useful for crystallization of other phospholipid interacting proteins as well as transmembrane proteins.