Structural insights into phosphopantetheinyl hydrolase PptH from Mycobacterium tuberculosis

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• The amidinourea 8918 drug targets Mycobacterium tuberculosis phosphopantetheinyl transferase (PptT).
• Resistance to 8918 emerged due to mutations in the adjacent rv2795c gene, encoding PptH.
• PptH acts antagonistically to PptT, functioning as a phosphopantetheinyl hydrolase.

Purpose of the Study:

• To elucidate the structure of Mtb's PptH, the first structurally characterized phosphopantetheinyl hydrolase.
• To understand the structural basis for PptH's role in 8918 resistance.
• To compare PptH with other phosphopantetheinyl hydrolases.

Main Methods:

• X-ray crystallography at 2.5 Å resolution.
• Structural similarity searches.
• Analysis of enzyme active sites and conserved residues.

Main Results:

• The crystal structure of Mtb PptH revealed a four-layer (α/β/β/α) sandwich fold.
• A Mn-Fe binuclear center was identified in the active site, characteristic of metallophosphoesterases.
• The structure rationalizes previously identified PptH mutations linked to 8918 resistance.
• PptH and E. coli AcpH represent distinct, convergently evolved phosphopantetheinyl hydrolase families.

Conclusions:

• The solved PptH structure provides crucial insights into its function and mechanism.
• Understanding PptH's structure and its interaction with PptT is vital for developing new anti-tuberculosis drugs.
• The study highlights the convergent evolution of phosphopantetheinyl hydrolases.