Structure of buffalo lactoferrin at 2.5 angstrom resolution using crystalsgrown at 303 K shows different orientations of the N and C lobes

The structure of buffalo lactoferrin has been determined at 303 K. The crys tals belong to orthorhombic space group P2(1)2(1)2(1), with unit-cell param eters a = 77.5, b = 91.0, c = 131.5 Angstrom and Z = 4. The structure has b een refined to an R factor of 0.187. The overall structure of the protein i s similar to its structure determined at 277 K in a different crystal form. However, the lobe orientations in the two structures differ by 9.0 degrees , suggesting significant inter-lobe flexibility in this family of proteins. The inter-lobe interactions are predominantly hydrophobic and could act as a cushion for a change in orientation under the influence of external cond itions. On the other hand, the domain arrangements are found to be similar in 277 and 303 K crystal structures, with orientations differing by 1.5 and 1.0 degrees in the N and C Iobes, respectively. The results of these inves tigations suggest that the increase in temperature helps in the production of better quality crystals.