Cook Erik C, Featherston Emily R, Showalter Scott A, Cotruvo Joseph A
Department of Chemistry , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States.
Department of Biochemistry and Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States.
Biochemistry. 2019 Jan 15;58(2):120-125. doi: 10.1021/acs.biochem.8b01019. Epub 2018 Nov 2.
Lanmodulin (LanM) is a high-affinity lanthanide (Ln)-binding protein recently identified in Methylobacterium extorquens, a bacterium that requires Lns for the function of at least two enzymes. LanM possesses four EF-hands, metal coordination motifs generally associated with Ca binding, but it undergoes a metal-dependent conformational change with a 100 million-fold selectivity for Lns and Y over Ca. Here we present the nuclear magnetic resonance solution structure of LanM complexed with Y. This structure reveals that LanM features an unusual fusion of adjacent EF-hands, resulting in a compact fold to the best of our knowledge unique among EF-hand-containing proteins. It also supports the importance of an additional carboxylate ligand in contributing to the protein's picomolar affinity for Lns, and it suggests a role of unusual N -H···N hydrogen bonds, in which LanM's unique EF-hand proline residues are engaged, in selective Ln recognition. This work sets the stage for a detailed mechanistic understanding of LanM's Ln selectivity, which may inspire new strategies for binding, detecting, and sequestering these technologically important metals.
镧调蛋白（LanM）是一种高亲和力的镧系元素（Ln）结合蛋白，最近在甲基营养型细菌中被发现，这种细菌的至少两种酶的功能需要镧系元素。LanM拥有四个EF手结构域，这是通常与钙结合相关的金属配位基序，但它会发生金属依赖性构象变化，对镧系元素和钇的选择性比对钙高1亿倍。在此，我们展示了与钇结合的LanM的核磁共振溶液结构。该结构表明，LanM具有相邻EF手结构域的异常融合，据我们所知，这在含EF手结构域的蛋白质中形成了一种独特的紧密折叠。它还支持了一个额外的羧酸盐配体对蛋白质与镧系元素皮摩尔亲和力的重要贡献，并暗示了异常的N-H···N氢键（LanM独特的EF手脯氨酸残基参与其中）在选择性镧系元素识别中的作用。这项工作为详细了解LanM的镧系元素选择性奠定了基础，这可能会激发新的策略来结合、检测和隔离这些具有重要技术意义的金属。
