Crystal structural studies of destripeptide (B28-B30) insulin

Abstract

Single crystals of destripeptide (B28-B30) insulin (DTRI) in three forms were obtained by hanging-drop vapor diffusion method. Form 1 belongs to P21 space group with cell parameters a =4.77 nm b =6.19 nm c =6.12 nm β =110.3o. Form 2 belongs to P4 1 22 or P4 3 22 space group with cell parameters a = 6.45 nm, c =12.07 nm. Form 3 belongs to P2 1 2 1 2 1 space group with cell parameters a =4.98 nm b =5.16 nm c =10.06 nm. The structure of form 1 crystal was determined by molecular replacement method and refined at 0.23 nm resolution. The R-factor of the final model is 18.8% with r.m.s. deviations of 0.001 5 nm and 3.3o for the bond lengths and the bond angles, respectively. Studies on the crystal structure show that the removal of B28 Pro has brought DTRI structural changes which made it dissociate more easily than native insulin although DTRI can still form a hexamer.