Cryo-EM structures of multiple-peptide resistance factor (MprF) from Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• MprF enzymes are bifunctional, catalyzing aminoacylation of lipid head groups and translocating modified lipids across bacterial membranes.
• Lipid modification by MprF is likely an adaptation to specific microbial environments.
• Understanding MprF structure-function is key to bacterial membrane biology.

Purpose of the Study:

• To determine the cryo-electron microscopy (cryo-EM) structures of the MprF enzyme from Pseudomonas aeruginosa.
• To elucidate the enzyme's architecture, conformational dynamics, and potential mechanisms of catalysis and lipid transport.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to obtain high-resolution structures of MprF in detergent micelle and nanodisc environments.
• Biochemical analyses were performed to validate the observed dimeric arrangement and structural features.

Main Results:

• The cryo-EM structures reveal a dimeric MprF enzyme with an architecture distinct from homologous Rhizobium MprF.
• Conformational changes in the synthase domain's terminal helix were observed, suggesting dynamic elements crucial for catalysis.
• Lipid-like densities indicate potential pathways for lipid transport between the synthase and transmembrane domains.

Conclusions:

• The dimeric structure of Pseudomonas aeruginosa MprF is validated, offering insights into its unique architecture.
• Dynamic structural elements within the synthase domain are proposed to play a mechanistic role in tRNA binding and lipid transport.
• The findings provide a structural basis for understanding the bifunctional mechanism of MprF enzymes.