Crystal Structures of the Acinetobacter baumannii Macrolide Phosphotransferase E

Area of Science:

• Microbiology
• Structural Biology
• Drug Resistance

Background:

• Acinetobacter baumannii is a significant cause of challenging clinical infections due to its multidrug resistance.
• The macrolide phosphotransferase gene (mphE) contributes to macrolide antibiotic resistance in A. baumannii.

Purpose of the Study:

• To determine the three-dimensional structure of the MphE protein involved in macrolide resistance.
• To elucidate the molecular mechanisms underlying MphE's catalytic activity and its role in drug resistance.

Main Methods:

• X-ray crystallography was used to determine the structures of MphE in apo, erythromycin-bound, and azithromycin-bound states.
• Structural analysis focused on the active site, bound ligands (erythromycin, azithromycin, GTP), and magnesium ions.

Main Results:

• The active state of MphE was captured, revealing the binding of guanosine triphosphate (GTP) and two magnesium ions with erythromycin.
• Magnesium ions were found to stabilize the MphE active site, facilitating phosphoryl group transfer.
• Conserved residues Asp29, Asp194, His199, and Asp213 were identified as crucial for MphE's catalytic phosphorylation.

Conclusions:

• The determined MphE structures provide molecular insights into macrolide resistance mechanisms in Acinetobacter baumannii.
• Understanding the role of specific residues and ions offers potential targets for developing improved macrolide antibiotics.