Characterization of the proline-utilization pathway in Mycobacterium tuberculosis through structural and functional...

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• The proline-utilization pathway in Mycobacterium tuberculosis (Mtb) is vital for Mtb persistence in vivo.
• This pathway represents a potential therapeutic target for tuberculosis (TB).
• Two enzymes, PruB and PruA, convert proline to glutamate in Mtb.

Purpose of the Study:

• To determine the three-dimensional structures of Mtb-PruA.
• To investigate the NAD(+) binding mode and active site characteristics of Mtb-PruA.
• To reconstitute and functionally validate the Mtb proline-utilization pathway in vitro.

Main Methods:

• X-ray crystallography was used to determine the structures of Mtb-PruA in apo and NAD(+) bound states.
• Recombinant PruA and PruB enzymes were expressed and purified.
• A novel NMR approach was employed for functional validation.

Main Results:

• The 3D structures of Mtb-PruA were resolved at 2.5 Å (apo) and 2.1 Å (NAD(+) complex).
• A conserved NAD(+) binding mode was identified, similar to related enzymes.
• Species-specific active site differences suggest selective Mtb-PruA inhibition is possible.
• The reconstituted pathway demonstrated PruA and PruB are sufficient for proline to glutamate conversion.

Conclusions:

• The structural and functional characterization of Mtb-PruA provides insights into the proline-utilization pathway.
• The findings support the development of selective inhibitors targeting Mtb-PruA for novel TB therapeutics.
• This study is the first to demonstrate the sufficiency of monofunctional proline-utilization enzymes in converting proline to glutamate.