Crystallization of the macromolecular complex transthyretin-retinol-binding protein.

Single crystals of the macromolecular complex transthyretin-retinol-binding protein have been obtained. Transthyretin is a carrier of the hormone thyroxine in plasma whereas retinol-binding protein is the specific transporter of the alcohol form of vitamin A in the same medium. This macromolecular complex is found under physiological conditions in plasma and is believed to play an important physiological role. The complex can be formed in vitro by proteins purified from different species. Our crystals are grown with chicken retinol-binding protein complexed to human transthyretin. They are grown by equilibrium dialysis versus 2.3 M ammonium sulphate, 3% ethylene glycol buffered with 0.1 M succinate (pH 5.5). Their space group is I222 (or I2(1)2(1)2(1)) with unit cell parameters a = 222.4 A, b = 163.4 A and c = 55.5 A. Using a conventional X-ray source, we have collected a complete data set of the crystals to a nominal resolution of 3.1 A.