Biochemical and structural characterization reveals Rv3400 codes for β-phosphoglucomutase in Mycobacterium...

Area of Science:

• Biochemistry and Molecular Biology
• Structural Biology
• Microbiology

Background:

• Mycobacterium tuberculosis (Mtb) utilizes diverse carbon sources, including maltose and trehalose, for survival and virulence.
• Key enzymes in Mtb's trehalose and maltose metabolism remain largely uncharacterized.
• The hypothetical gene Rv3400 was investigated for its role in Mtb's metabolic pathways.

Purpose of the Study:

• To structurally and functionally characterize the conserved hypothetical protein Rv3400 from Mycobacterium tuberculosis.
• To determine the enzymatic activity of Rv3400 and its role in Mtb physiology.
• To elucidate the structural basis and key residues involved in Rv3400's catalytic function.

Main Methods:

• Crystallization of Rv3400 and determination of its 3D structure at 1.7 Å resolution.
• Comparative structural analysis to predict potential enzymatic activities.
• Biochemical assays to confirm β-phosphoglucomutase (β-PGM) activity and metal ion dependency.
• Site-directed mutagenesis to identify critical residues for enzyme function.

Main Results:

• Rv3400 adopts a Rossmann fold, structurally similar to haloacid dehalogenase family proteins.
• Rv3400 was confirmed to possess β-phosphoglucomutase (β-PGM) activity, converting β-D-glucose-1-phosphate to β-D-glucose-6-phosphate.
• The enzyme is metal-dependent, with specific aspartate residues (D29 and D31) in the DxD motif being essential for activity.

Conclusions:

• Rv3400 encodes the β-phosphoglucomutase (β-PGM) enzyme in Mycobacterium tuberculosis.
• Mtb β-PGM plays a vital role in carbohydrate metabolism, supplying glucose-6-phosphate for ATP and NADPH generation.
• Understanding Rv3400's function provides insights into Mtb's metabolic adaptability and potential therapeutic targets.