Evidence to Suggest Bacterial Lipoprotein Diacylglyceryl Transferase (Lgt) is a Weakly Associated Inner Membrane Protein

• Published in: The Journal of membrane biology 2019-12, Vol.252 (6), p.563-575
• Main Authors: Sangith, Nikhil, Kumar, Subramani, Sankaran, Krishnan
• Format: Article
• Language: English
• Subjects: Antibiotics; Biochemistry; Biomedical and Life Sciences; Biosynthesis; Catalysis; Computer applications; Crystal structure; Docking; Helices; Human Physiology; Hydrophobicity; Life Sciences; Lipids; Membrane proteins; Phosphatidylglycerol; Phospholipids; Post-translation; Protein biosynthesis; Proteins; Proteolysis; Secretion; Software; Solubilization; Spheroplasts
• ISSN: 0022-2631; 1432-1424
• DOI: 10.1007/s00232-019-00076-3

The unique and ubiquitous bacterial lipoprotein biosynthesis pathway is an attractive new antibiotic target. Crystal structures of its three biosynthetic enzymes have been solved recently. The first enzyme, Phosphatidylglycerol:proLipoprotein diacylglyceryl Transferase (Lgt), which initiates the post-translational modification at the metabolic interface of protein biosynthesis, phospholipid biosynthesis, protein secretion and lipid modification was reported to be a seven-transmembrane helical structure with a catalytic periplasmic head. Its complete solubilization in water or mild detergent in a fully active state, its chromatographic behaviour as an active monomer in the absence of detergent and recovery of active whole-length protein after proteolytic treatment of spheroplasts cast serious doubts about its proposed membrane association and orientation. Rather, it could be a seven-helical bundle partially embedded in the inner membrane’s inner leaflet aided by hydrophobic interaction. In fact, there are examples where originally reported seven-transmembrane proteins were later shown to be seven-helical peripheral membrane proteins based on solubilization criterion and re-analysis. Validated computational tool, Membrane Optimal Docking Area (MODA), also predicted a weaker association of Lgt’s helices with the membrane compared to typical transmembrane proteins. This insight is crucial to Lgt-based antibiotic design.