Dickmanns Achim, Schmidt Bernhard, Rudolph Markus G, Mariappan Malaiyalam, Dierks Thomas, von Figura Kurt, Ficner Ralf
Abteilung Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität, Justus-von-Liebig Weg 9, D-37077 Göttingen, Germany.
J Biol Chem. 2005 Apr 15;280(15):15180-7. doi: 10.1074/jbc.M414317200. Epub 2005 Feb 1.
In eukaryotes, sulfate esters are degraded by sulfatases, which possess a unique Calpha-formylglycine residue in their active site. The defect in post-translational formation of the Calpha-formylglycine residue causes a severe lysosomal storage disorder in humans. Recently, FGE (formylglycine-generating enzyme) has been identified as the protein required for this specific modification. Using sequence comparisons, a protein homologous to FGE was found and denoted pFGE (paralog of FGE). pFGE binds a sulfatase-derived peptide bearing the FGE recognition motif, but it lacks formylglycine-generating activity. Both proteins belong to a large family of pro- and eukaryotic proteins containing the DUF323 domain, a formylglycine-generating enzyme domain of unknown three-dimensional structure. We have crystallized the glycosylated human pFGE and determined its crystal structure at a resolution of 1.86 A. The structure reveals a novel fold, which we denote the FGE fold and which therefore serves as a paradigm for the DUF323 domain. It is characterized by an asymmetric partitioning of secondary structure elements and is stabilized by two calcium cations. A deep cleft on the surface of pFGE most likely represents the sulfatase polypeptide binding site. The asymmetric unit of the pFGE crystal contains a homodimer. The putative peptide binding site is buried between the monomers, indicating a biological significance of the dimer. The structure suggests the capability of pFGE to form a heterodimer with FGE.
在真核生物中，硫酸酯由硫酸酯酶降解，这些酶在其活性位点含有独特的α-甲酰甘氨酸残基。α-甲酰甘氨酸残基翻译后形成过程中的缺陷会导致人类严重的溶酶体贮积症。最近，甲酰甘氨酸生成酶（FGE）已被确定为这种特定修饰所需的蛋白质。通过序列比较，发现了一种与FGE同源的蛋白质，并将其命名为pFGE（FGE的旁系同源物）。pFGE能结合带有FGE识别基序的硫酸酯酶衍生肽段，但它缺乏甲酰甘氨酸生成活性。这两种蛋白质都属于一个包含DUF323结构域的原核和真核蛋白质大家族，DUF323结构域是一种三维结构未知的甲酰甘氨酸生成酶结构域。我们已使糖基化的人pFGE结晶，并以1.86 Å的分辨率确定了其晶体结构。该结构揭示了一种新的折叠方式，我们将其称为FGE折叠，因此它是DUF323结构域的范例。其特征是二级结构元件的不对称分布，并由两个钙阳离子稳定。pFGE表面的一个深裂缝很可能代表硫酸酯酶多肽结合位点。pFGE晶体的不对称单元包含一个同二聚体。假定的肽结合位点埋藏在单体之间，表明二聚体具有生物学意义。该结构表明pFGE有能力与FGE形成异二聚体。
