Mycobacterium tuberculosis acyl carrier protein synthase adopts two different pH-dependent structural conformations

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• Acyl carrier protein synthase (AcpS) is crucial for fatty acid biosynthesis.
• Understanding AcpS structure and function is key to developing novel antimicrobials.
• Previous studies have reported the structure of AcpS-ADP complex.

Purpose of the Study:

• To determine the crystal structures of AcpS from Mycobacterium tuberculosis (Mtb) and Corynebacterium ammoniagenes.
• To investigate the pH-dependent conformational changes and activity of AcpS.
• To compare the structures of apo-AcpS and AcpS-ADP complexes.

Main Methods:

• X-ray crystallography was used to determine the crystal structures of Mtb AcpS and C. ammoniagenes AcpS.
• Biochemical assays were performed to assess AcpS activity at different pH values.
• Structural comparisons were made between apo-AcpS and AcpS-ADP structures.

Main Results:

• Mtb AcpS and C. ammoniagenes AcpS were crystallized at pH 5.3 and 6.5, respectively.
• AcpS adopts different conformations at varying pH values, with significant structural changes observed at pH 6.5.
• In vitro experiments demonstrated higher AcpS activity between pH 4.4 and 6.0, with a notable drop above pH 6.5 due to conformational changes.

Conclusions:

• Apo-AcpS and AcpS-ADP exist in distinct conformations influenced by crystallization pH.
• pH-dependent conformational changes directly impact AcpS activity.
• These findings provide insights into the regulation of AcpS function and potential therapeutic targets.