Residue-Dependent Thermodynamic Cost and Barrel Plasticity Balances Activity in the PhoPQ-Activated Enzyme PagP of Salmonella typhimurium.
PagP is an eight-stranded transmembrane β-barrel enzyme indispensable for lipid A palmitoylation in Gram-negative bacteria. The severity of infection by pathogens, including Salmonella, Legionella, and Bordetella, and resistance to antimicrobial peptides, relies on lipid A remodeling by PagP, rendering PagP a sought-after drug target. Despite a conserved sequence, more robust palmitoylation of lipid A is observed in Salmonella typhimurium compared to Escherichia coli, a possible consequence of the differential regulation of PagP expression and/or specific activity. Work here identifies molecular signatures that demarcate thermodynamic stability and variances in catalytic efficiency between S. typhimurium (PagP-St) and E. coli (PagP-Ec) transmembrane PagP barrel variants. We demonstrate that Salmonella PagP displays a 2-fold destabilization of the barrel, while achieving 15-20 magnitude higher lipase efficiency, through subtle alterations of lipid-facing residues distal from the active site. We find that catalytic properties of these homologues are retained across different lipid environments such as micelles, vesicles, and natural extracts. By comparing thermodynamic stability with activity of selectively designed mutants, we conclude that activity-stability trade-offs can be influenced by factors secluded from the catalytic region. Our results provide a compelling correlation of the primary protein structure with enzymatic activity, barrel thermodynamic stability, and scaffold plasticity. Our analysis can open avenues for the development of potent pharmaceuticals against salmonellosis.
Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research , Bhopal 462023, India.
Bharat Ramasubramanian
BR
Iyer
Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research , Bhopal 462023, India.
Radhakrishnan
R
Mahalakshmi
D000217:Acyltransferases / Q000737:chemistry* / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D004795:Enzyme Stability; D029968:Escherichia coli Proteins / Q000737:chemistry; D008049:Lipase / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics; D013816:Thermodynamics
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D000217:Acyltransferases; C468520:PagP protein, E coli; D008049:Lipase