Molecular insights into the functional mechanism of phosphoserine phosphatase SerB2 in Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb) phosphoserine phosphatase SerB2 is a key enzyme essential for bacterial survival and virulence, catalyzing the final step in the L-serine biosynthesis pathway. SerB2 is an attractive drug target due to its role in immune evasion by Mtb. However, the functional mechanism of Mtb SerB2 remains poorly understood. Here, we measured the hydrodynamic radius of monomeric SerB2 to be 5.4 ± 0.3 nm. Based on an AlphaFold2-predicted structural model, molecular docking was performed and site-specific mutations were carried out. Mutants D185A, D187A, E194A, S226A, R230A or K318A exhibited significantly reduced activity. In contrast, deletion of segment 294-314 (Δ294-314) increased activity. Notably, the 294-314 region exhibited higher flexibility compared to other parts of SerB2. Among the inhibitors tested, clofazimine displayed the most potent inhibitory effect. Our findings offer new insights into the mechanisms of SerB2 function and lay the structural and biochemical groundwork for developing novel anti-tuberculosis therapies.