Appel C Denise, Feld Geoffrey K, Wallace Bret D, Williams R Scott
Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, 27709.
Protein Sci. 2016 Sep;25(9):1682-91. doi: 10.1002/pro.2974. Epub 2016 Jul 7.
Cells use the post-translational modification ADP-ribosylation to control a host of biological activities. In some pathogenic bacteria, an operon-encoded mono-ADP-ribosylation cycle mediates response to host-induced oxidative stress. In this system, reversible mono ADP-ribosylation of a lipoylated target protein represses oxidative stress response. An NAD(+) -dependent sirtuin catalyzes the single ADP-ribose (ADPr) addition, while a linked macrodomain-containing protein removes the ADPr. Here we report the crystal structure of the sitruin-linked macrodomain protein from Staphylococcus aureus, SauMacro (also known as SAV0325) to 1.75-Å resolution. The monomeric SauMacro bears a previously unidentified Zn(2+) -binding site that putatively aids in substrate recognition and catalysis. An amino-terminal three-helix bundle motif unique to this class of macrodomain proteins provides a structural scaffold for the Zn(2+) site. Structural features of the enzyme further indicate a cleft proximal to the Zn(2+) binding site appears well suited for ADPr binding, while a deep hydrophobic channel in the protein core is suitable for binding the lipoate of the lipoylated protein target.
细胞利用翻译后修饰——ADP核糖基化来控制一系列生物活性。在一些致病细菌中，一个操纵子编码的单ADP核糖基化循环介导对宿主诱导的氧化应激的反应。在这个系统中，脂酰化靶蛋白的可逆单ADP核糖基化抑制氧化应激反应。一种依赖NAD(+)的沉默调节蛋白催化单ADP核糖（ADPr）的添加，而一种与之相连的含宏结构域的蛋白则去除ADPr。在此，我们报道了来自金黄色葡萄球菌的沉默调节蛋白连接的宏结构域蛋白SauMacro（也称为SAV0325）的晶体结构，分辨率为1.75 Å。单体的SauMacro具有一个先前未被识别的锌（Zn(2+)）结合位点，推测该位点有助于底物识别和催化。这类宏结构域蛋白特有的氨基末端三螺旋束基序为锌（Zn(2+)）位点提供了一个结构支架。该酶的结构特征进一步表明，锌（Zn(2+)）结合位点附近的一个裂缝似乎非常适合ADPr结合，而蛋白核心中的一个深疏水通道则适合结合脂酰化蛋白靶标的硫辛酸。
