Purification, crystallization and preliminary crystallographic analysis of mare lactoferrin

Lactoferrin is an iron-binding glycoprotein with a molecular weight of 80 kDa. The protein has two iron binding sites. It has two structural lobes, each housing one Fe³⁺ and the synergistic CO₃^2- ion. The protein was isolated from the colostrum/milk of mares maintained at National Research Centre on Equines, Hisar, India. The purified samples of the protein were crystallized using a microdialysis method. The protein was dialysed against low ionic strength buffer solution. Several crystal forms were obtained, out of which three were characterized which have cell dimensions as follows. Form I a = 79.8, b = 103.5, c = 112.0 Å, space group P2₁2₁2₁, with one protein molecule per asymmetric unit and a solvent content of 57%. Form II a = 84.9, b = 99.7, c = 103.5 Å, space group P2₁2₁2₁ with one molecule per asymmetric unit and a solvent content of 55%. Form III a = 151.0, b = 151.0, c = 240.6 Å, space group P4₁2₁2 with three molecules in the asymmetric unit and a solvent content of 57%. The intensity data up to 3.8 Å resolution for form I, 2.9 Å resolution data for form II and 6 Å resolution data for form III have been collected. Further calculations are in progress.