S. Karthikeyan et al., Structure of buffalo lactoferrin at 2.5 angstrom resolution using crystalsgrown at 303 K shows different orientations of the N and C lobes, ACT CRYST D, 55, 1999, pp. 1805-1813
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.