Kumar Pravindra, Yadav Savita, Singh Tej P
Department of Biophysics, All India Institute of Medical Sciences, New Delhi 110 029.
Indian J Biochem Biophys. 2002 Feb;39(1):16-21.
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.
乳铁蛋白从新鲜的山羊初乳样品中纯化出来，用Fe3+和CO3(2-)离子饱和，并通过微透析法结晶。晶体属于正交晶系空间群P2(1)2(1)2(1)，a = 104.6 Å，b = 153.8 Å，c = 155.1 Å，Z = 4。晶体质量较差，因此强度数据仅限制在4.0 Å分辨率。结构通过分子置换法确定，使用双铁水牛乳铁蛋白作为模型。该溶液清楚地表明在不对称单元中存在一个分子，这对应于7.1 Å3/Da的Vm值。使用15870个从15,870到4.0 Å分辨率的所有反射，通过严格约束将结构精修至R因子为0.246。山羊乳铁蛋白的整体结构与水牛和牛乳铁蛋白的基本相似。然而，山羊乳铁蛋白中铁结合环境有所不同，其中2个CO3(2-)离子占有率较低。在当前情况下，约84%的溶剂含量非常高，这解释了山羊乳铁蛋白晶体的易碎性。在某种程度上，尽管已报道过溶剂含量高达89%的晶体，但晶体竟然还能生长，这非常令人惊讶。
