Crystallization and structure determination of goat lactoferrin at 4.0 A resolution: a new form of packing in lactoferrins with a high solvent content in crystals.
Lactoferrin was purified from fresh samples of goat colostrums, saturated with Fe3+ and CO3(2-) ions and crystallized by microdialysis method. The crystals belong to orthorhombic space group P2(1)2(1)2(1) with a=104.6 A, b=153.8 A, c=155.1 A and Z=4. The quality of crystals was poor, thus the intensity data were restricted to 4.0 A resolution only. The structure was determined by molecular replacement method using diferric buffalo lactoferrin as a model. The solution clearly indicated the presence of one molecule in the asymmetric unit, which corresponds to a Vm value of 7.1 A3/Da. The structure was refined with stringent constraints to an R-factor of 0.246 using all the reflections 15,870 to 4.0 A resolution. The overall structure of goat lactoferrin is essentially similar to those of buffalo and bovine lactoferrins. However, the iron-binding environment in goat lactoferrin is somewhat different, in which 2 CO3(2-). ions have low occupancies. The solvent content of approximately 84% was very high in the present case which explains the fragility of the crystals of goat lactoferrin. In a way, it is very surprising that the crystals grow at all, although crystals with solvent as high as 89% have been reported.
Department of Biophysics, All India Institute of Medical Sciences, New Delhi 110 029.
Pravindra
P
Kumar
Savita
S
Yadav
Tej P
TP
Singh
D000818:Animals; D000838:Anions / Q000737:chemistry; D001665:Binding Sites; D003126:Colostrum / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D006041:Goats; D007501:Iron / Q000737:chemistry; D007781:Lactoferrin / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012997:Solvents
D000838:Anions; D008670:Metals; D012997:Solvents; D007501:Iron; D007781:Lactoferrin