High resolution crystal structures of amphibian red-cell L ferritin: potential roles for structural plasticity and solvation in function.
High resolution crystal structures of amphibian red-cell L ferritin: potential roles for structural plasticity and solvation in function.
复制标题
两栖动物红细胞 L 铁蛋白的高分辨率晶体结构：结构可塑性和功能溶剂化的潜在作用。
DOI：
10.1006/jmbi.1995.0274
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Allewell,NM
中科院分区：
文献类型：
--
作者：
Trikha,J;Theil,EC;Allewell,NM
铁蛋白是一种在动物、植物和微生物中高度保守的多亚基蛋白质，它以立方对称的方式聚集在一起，并将水合铁离子和质子输送到蛋白质内部的矿化核心。本文报道了重组两栖动物红细胞L铁蛋白及其两个突变体在两种条件下的高分辨结构。在一个突变体中，Glu56、57、58和60被Ala取代，导致铁吸收动力学的滞后期。在第二个突变体中，His25被替换为Tyr，最多的是对功能产生了微妙的影响。用于提纯的甜菜碱分子结合在最近发现的细菌铁蛋白和马脾L铁蛋白的血红素结合部位附近的2倍轴上的所有结构中。对这五种两栖动物结构的比较发现，分子中的两个区域的构象柔性可能与功能有关。一组10到18个侧链的位置和相互作用对溶液条件和Glu→Ala突变都很敏感，其中大部分位于蛋白质的内表面。这些侧链的一个子集和有序的溶剂分子链从Glu56到58和Glu60附近延伸到野生型蛋白质中的3倍通道，并可能参与铁或质子的运输。在谷氨酸→丙氨酸突变体中，“水合脊椎”被破坏。相反，H25Y突变使主链原子的位置在突变位置和整个结构中的4倍轴和侧链位置之间移动；主链原子的位置变化最大的是DE环和E螺旋，距离突变位置约10ä。综上所述，这些结果表明溶剂化、结构可塑性和协同结构变化可能在铁蛋白的功能中起作用。类似的离子通道蛋白的结构和功能，如膜联蛋白被注意到。
Ferritin is a highly conserved multisubunit protein in animals, plants and microbes which assembles with cubic symmetry and transports hydrated iron ions and protons to and from a mineralized core in the protein interior. We report here the high resolution structures of recombinant amphibian red-cell L ferritin and two mutants solved under two sets of conditions. In one mutant, Glu56, 57, 58 and 60 were replaced with Ala, producing a lag phase in the kinetics of iron uptake. In the second mutant, His25 was replaced with Tyr with, at most, subtle effects on function. A molecule of betaine, used in the purification, is bound in all structures at the 2-fold axis near the recently identified heme binding site of bacterioferritin and horse spleen L ferritin. Comparisons of the five amphibian structures identify two regions of the molecule in which conformational flexibility may be related to function. The positions and interactions of a set of 10 to 18 side-chains, most of which are on the inner surface of the protein, are sensitive both to solution conditions and to the Glu→Ala mutation. A subset of these side-chains and a chain of ordered solvent molecules extends from the vicinity of Glu56 to 58 and Glu60 to the 3-fold channel in the wild type protein and may be involved in the transport of either iron or protons. The “spine of hydration” is disrupted in the Glu→Ala mutant. In contrast, H25Y mutation shifts the positions of backbone atoms between the site of the mutation and the 4-fold axis and side-chain positions throughout the structure; the largest changes in the position of backbone atoms are in the DE loop and E Helix, approximately 10 Å from the mutation site. In combination, these results indicate that solvation, structural plasticity and cooperative structural changes may play a role in ferritin function. Analogies with the structure and function of ion channel proteins such as annexins are noted.