X-RAY STRUCTURAL STUDIES OF LACTOFERRIN

我们的目的是为了更好地了解分子基础 乳铁蛋白是牛奶中主要的铁结合蛋白，在乳汁中的生物学作用 许多其他身体分泌物，以及白细胞中的。这将解决其 抗菌性能及其摄取和释放机制 金属离子。这将对理解身体有重要的影响。 防御机制，特别是母乳的生物学和 微量元素的生物可利用性。 (I)具体地说，人乳铁蛋白的三维结构将 用X射线结晶学在高分辨率下测定。该结构 然后会被提炼，这样就可以准确地确定铁元素的性质， 在蛋白质结构中的位置和可及性，以及 可以明确地确定具有重要功能的阴离子(HCO3离子)。 高分辨率分析将建立在已经进行的初步研究的基础上 被执行。乳铁蛋白的大晶体，对X射线很稳定， 已经得到了；重原子衍生物已经制备出来， 在6A和3.5A下的X射线研究给出了有希望的 结果。 (Ii)一旦确定了高分辨率结构，就具有约束力 研究将与其他金属离子(如锌、铜、钙、 Cr3，Mn2)和阴离子(如草酸)可以结合在特定的 铁的地点或非特定地点。这将有助于确定 乳铁蛋白与牛奶中微量元素的结合及对其影响 生物利用度。 (3)该结构还将用于检查结构和功能 与其他铁结合蛋白的关系，特别是血清转铁蛋白， 血浆中的铁转运蛋白和卵转铁蛋白。 (Iv)脱脂乳铁蛋白，乳铁蛋白的铁结合片段，以及 其他物种(如牛)的乳铁蛋白将在比较中进行检测 学习。 (V)作为长期目标，将通过以下途径审查该结构 目前由其他组织发起的定点突变研究 研究人员。

Our aim is to gain a better understanding of the molecular basis for the biological roles of lactoferrin, the major iron-binding protein in milk, in many other bodily secretions, and in leukocytes. This will address its antibacterial properties, as well as mechanisms of uptake and release o metal ions. It will have important implications for understanding bodily defence mechanisms and in particular the biology of human milk and the bioavailability of trace elements. (i) Specifically, the three-dimensional structure of human lactoferrin will be determined at high resolution by X-ray crystallography. The structure will then be refined, so that the exact nature of the iron sites, their location and accessibility in the protein structure, and the role of functionally important anions (HCO3 ion) can be unambiguously determined. The high resolution analysis will build upon preliminary studies already carried out. Large crystals of lactoferrin, which are stable to X-rays, have been obtained; heavy atom derivatives have been prepared and characterised; and X-ray studies at 6A and 3.5A have given promising results. (ii) Once the high resolution structure has been determined, binding studies will be carried out with other metal ions (eg Zn2+, Cu2+, Ca2+, Cr3+, Mn2+) and anions (eg oxalate) which may bind either in the specific iron sites or in non-specific sites. This will help define the role of lactoferrin in binding trace element in milk, and in influencing their bioavailability. (iii) The structure will also be used to examine structural and functional relationships with other iron-binding proteins, notably serum transferrin, the iron transport protein in plasma, and ovotransferrin. (iv) Apolactoferrin, iron-binding fragments of lactoferrin, and lactoferrins of other species (e.g. bovine) will be examined in comparative studies. (v) As a long-term aim, the structure will be examined through site-directed mutagenesis studies presently being initiated by other researchers.