Baumgartner Jackson, Lee Jesi, Halavaty Andrei S, Minasov George, Anderson Wayne F, Kuhn Misty L
Department of Chemistry and Biochemistry, San Francisco State University, USA.
Department of Biochemistry and Molecular Genetics, Northwestern University Feinberg School of Medicine, USA.
Acta Crystallogr F Struct Biol Commun. 2017 Nov 1;73(Pt 11):621-628. doi: 10.1107/S2053230X17015357. Epub 2017 Oct 30.
L-Rhamnose is a ubiquitous bacterial cell-wall component. The biosynthetic pathway for its precursor dTDP-L-rhamnose is not present in humans, which makes the enzymes of the pathway potential drug targets. In this study, the three-dimensional structure of the first protein of this pathway, glucose-1-phosphate thymidylyltransferase (RfbA), from Bacillus anthracis was determined. In other organisms this enzyme is referred to as RmlA. RfbA was co-crystallized with the products of the enzymatic reaction, dTDP-α-D-glucose and pyrophosphate, and its structure was determined at 2.3 Å resolution. This is the first reported thymidylyltransferase structure from a Gram-positive bacterium. RfbA shares overall structural characteristics with known RmlA homologs. However, RfbA exhibits a shorter sequence at its C-terminus, which results in the absence of three α-helices involved in allosteric site formation. Consequently, RfbA was observed to exhibit a quaternary structure that is unique among currently reported glucose-1-phosphate thymidylyltransferase bacterial homologs. These structural analyses suggest that RfbA may not be allosterically regulated in some organisms and is structurally distinct from other RmlA homologs.
L-鼠李糖是一种普遍存在的细菌细胞壁成分。其前体dTDP-L-鼠李糖的生物合成途径在人体内并不存在，这使得该途径中的酶成为潜在的药物靶点。在本研究中，测定了炭疽芽孢杆菌中该途径第一种蛋白质——葡萄糖-1-磷酸胸苷酰转移酶（RfbA）的三维结构。在其他生物体中，这种酶被称为RmlA。RfbA与酶促反应产物dTDP-α-D-葡萄糖和焦磷酸共结晶，并在2.3 Å分辨率下确定了其结构。这是首次报道的革兰氏阳性细菌胸苷酰转移酶结构。RfbA与已知的RmlA同源物具有总体结构特征。然而，RfbA在其C末端表现出较短的序列，这导致参与变构位点形成的三个α螺旋缺失。因此，观察到RfbA表现出一种在目前报道的葡萄糖-1-磷酸胸苷酰转移酶细菌同源物中独特的四级结构。这些结构分析表明，RfbA在某些生物体中可能不受变构调节，并且在结构上与其他RmlA同源物不同。
