Studies on the crystal structure of A1-(D-Tryptophan) insulin.

We have determined the crystal structure of A1-(D-Trp) insulin and discovered that it belongs to the trigonal system with space group R3. The parameters of the unit cell are a = b = 78.6 A, c = 50.0 A. A set of data for half a sphere reciprocal space to a spacing of 2.2 A were collected. The model was adjusted and refined by using a step-by-step approach and a stereochemically-restrained least squares program, assisted by manual revision based on the difference Fourier maps, to a final R-factor of 0.218. The main and side chains of both A1-D-Trp residues in the asymmetric unit are well ordered. The packing of A1-(D-Trp) insulin in the unit cell, the conformational differences with other insulin structures and its structure and function relationship have also been discussed.