title: Characterization of M. tuberculosis SerB2, an essential HAD-family phosphatase, reveals novel properties.
abstract: M. tuberculosis harbors an essential phosphoserine phosphatase (MtSerB2, Rv3042c) that contains two small- molecule binding ACT-domains (Pfam 01842) at the N-terminus followed by the phosphoserine phosphatase (PSP) domain. We found that exogenously added MtSerB2 elicits microtubule rearrangements in THP-1 cells. Mutational analysis demonstrates that phosphatase activity is co-related to the elicited rearrangements, while addition of the ACT-domains alone elicits no rearrangements. The enzyme is dimeric, exhibits divalent metal- ion dependency, and is more specific for l- phosphoserine unlike other classical PSPases. Binding of a variety of amino acids to the ACT-domains influences MtSerB2 activity by either acting as activators/inhibitors/have no effects. Additionally, reduced activity of the PSP domain can be enhanced by equimolar addition of the ACT domains. Further, we identified that G18 and G108 of the respective ACT-domains are necessary for ligand-binding and their mutations to G18A and G108A abolish the binding of ligands like l- serine. A specific transition to higher order oligomers is observed upon the addition of l- serine at ∼0.8 molar ratio as supported by Isothermal calorimetry and Size exclusion chromatography experiments. Mutational analysis shows that the transition is dependent on binding of l- serine to the ACT-domains. Furthermore, the higher-order oligomeric form of MtSerB2 is inactive, suggesting that its formation is a mechanism for feedback control of enzyme activity. Inhibition studies involving over eight inhibitors, MtSerB2, and the PSP domain respectively, suggests that targeting the ACT-domains can be an effective strategy for the development of inhibitors.
authors.affiliation: Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, Uttar Pradesh, 226031, India.
authors.forename: Gaya Prasad
authors.initials: GP
authors.lastname: Yadav
authors.affiliation: Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, Uttar Pradesh, 226031, India.
authors.forename: Sonal
authors.initials: S
authors.lastname: Shree
authors.affiliation: Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, Uttar Pradesh, 226031, India.
authors.forename: Ruchi
authors.initials: R
authors.lastname: Maurya
authors.affiliation: Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, Uttar Pradesh, 226031, India.
authors.forename: Niyati
authors.initials: N
authors.lastname: Rai
authors.affiliation: Microbiology Division, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, Uttar Pradesh, 226031, India.
authors.forename: Diwakar Kumar
authors.initials: DK
authors.lastname: Singh
authors.affiliation: Microbiology Division, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, Uttar Pradesh, 226031, India.
authors.forename: Kishore Kumar
authors.initials: KK
authors.lastname: Srivastava
authors.affiliation: Molecular and Structural Biology Division, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow, Uttar Pradesh, 226031, India.
authors.forename: Ravishankar
authors.initials: R
authors.lastname: Ramachandran
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004791:Enzyme Inhibitors / Q000494:pharmacology; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding
chemical_list: D004791:Enzyme Inhibitors; D010744:Phosphoric Monoester Hydrolases; C022394:phosphoserine phosphatase