Structure-based mechanism of lipoteichoic acid synthesis by Staphylococcus aureus LtaS

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 5; pp. 1584 - 1589
• Main Authors: Lu, Duo, Wörmann, Mirka E, Zhang, Xiaodong, Schneewind, Olaf, Gründling, Angelika, Freemont, Paul S
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 03.02.2009; National Acad Sciences
• Subjects: Active sites; Amino acids; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - physiology; Binding sites; Biological Sciences; Catalytic Domain; Cell walls; Cells; Crystal structure; Enzymes; Hydrolysis; Infections; Lipopolysaccharides - biosynthesis; Manganese - metabolism; Membranes; Models, Molecular; Mutagenesis, Site-Directed; Phosphates; Plasmids; Protein Conformation; Protein synthesis; Proteins; Reaction mechanisms; Staphylococcus aureus; Staphylococcus aureus - metabolism; Staphylococcus infections; Teichoic Acids - biosynthesis
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0809020106

Staphylococcus aureus synthesizes polyglycerol-phosphate lipoteichoic acid (LTA) from phosphatidylglycerol. LtaS, a predicted membrane protein with 5 N-terminal transmembrane helices followed by a large extracellular part (eLtaS), is required for staphylococcal growth and LTA synthesis. Here, we report the first crystal structure of the eLtaS domain at 1.2-Å resolution and show that it assumes a sulfatase-like fold with an α/β core and a C-terminal part composed of 4 anti-parallel β-strands and a long α-helix. Overlaying eLtaS with sulfatase structures identified active site residues, which were confirmed by alanine substitution mutagenesis and in vivo enzyme function assays. The cocrystal structure with glycerol-phosphate and the coordination of a Mn²⁺ cation allowed us to propose a reaction mechanism, whereby the active site threonine of LtaS functions as nucleophile for phosphatidylglycerol hydrolysis and formation of a covalent threonine-glycerolphosphate intermediate. These results will aid in the development of LtaS-specific inhibitors for S. aureus and many other Gram-positive pathogens.