Structural analysis of desheptapeptide(B24-B30) insulin by molecular replacement

Desheptapeptide (B24 B30) insulin (DHPI), a virtually inactive insulin analog, has been crystallized in space group P2\-12\-12\-1 with two DHPI molecules in an asymmetric unit. The orientations and positions of the molecules were determined by molecular replacement, and a structural model was built at 0.3 nm resolution. The current model shows that the two DHPI monomers are related by a non crystallographic 2 fold axis, nearly parallel to the crystallographic c axis. This structural feature complicated the determination of the orientation of the local 2 fold axis, which was later confirmed by analysing the diffraction data of DHPI crystals.