Structural Insights into the Staphylococcus aureus DltC-Mediated D-Alanine Transfer

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Staphylococcus aureus is a significant pathogen causing challenging infections due to antibiotic resistance.
• D-alanylation of teichoic acids (TA) in S. aureus reduces cell envelope negative charge, enhancing resistance to antibiotics, especially cationic antimicrobial peptides.
• The dltABCD operon encodes essential proteins for D-alanine transfer to TA.

Purpose of the Study:

• To determine the crystal structure of Staphylococcus aureus DltC, a D-alanyl carrier protein.
• To analyze the interaction between S. aureus DltC and DltA using computational methods.
• To identify critical interface residues for DltA-DltC interaction and catalytic activity.

Main Methods:

• X-ray crystallography to determine the structure of S. aureus DltC.
• AlphaFold3 and all-atom molecular dynamics simulations to analyze protein-protein interactions.
• Site-directed mutagenesis to investigate the functional impact of interface residue substitutions.

Main Results:

• The first crystal structure of S. aureus DltC was determined.
• Computational analysis revealed key interactions between S. aureus DltA and DltC.
• Mutations at the DltA-DltC interface abolished DltC-mediated enhancement of DltA catalysis, highlighting its functional importance.

Conclusions:

• A catalytically critical interface between S. aureus DltA and DltC was defined.
• Structural insights into the D-alanylation pathway provide a basis for developing novel anti-Staphylococcus strategies.
• Targeting the D-alanylation pathway presents a potential avenue to overcome S. aureus antibiotic resistance.