Mycobacterium tuberculosis Protein Tyrosine Phosphatase PtpB Structure Reveals a Diverged Fold and a Buried Active Site

Abstract

Intracellular pathogenic bacteria manipulate host signal transduction pathways to facilitate infection. Mycobacterium tuberculosis protein tyrosine phosphatases (PTPs) PtpA and PtpB are thought to be secreted into host cells and interfere with unidentified signals. To illuminate the mechanisms of regulation and substrate recognition, we determined the 1.7 A resolution crystal structure of PtpB in complex with the product phosphate. The protein adopts a simplified PTP fold, which combines features of the conventional PTPs and dual-specificity phosphatases. PtpB shows two unusual elaborations--a disordered, acidic loop and a flexible, two-helix lid that covers the active site--that are specific to mycobacterial orthologs. Biochemical studies suggest that substrate mimicry in the lid may protect the phosphatase from oxidative inactivation. The insertion and deletion of large structural elements in PtpB suggest that, outside the active site module, the PTP family is under unusual selective pressure that promotes changes in overall structure.

Structural insights into mode of actions of novel natural Mycobacterium protein tyrosine phosphatase B inhibitors

“…The crystal structure of protein tyrosine phosphatase B of Mtb origin was obtained from Protein Data Bank [PDB ID: 1YWF] [15]. The protein structure was pre-processed by removing water molecules and all non-bonded heteroatoms using Accelyrs Viewerlite 5.0 [16].…”

“…Presence of histidine just before the active site cysteine makes it a better nucleophile. Therefore, residues His 160-Arg 166 constitute the active site of mPTPB [19]. Prepared natural compounds were subjected to docking using Glide's extra precision docking protocol.…”

Expression of Mycobacterium tuberculosis Protein Tyrosine Phosphatase B in Escherichia coli and Its Recovery from Inclusion Body

“…This expression system has a long time been established after pioneering work by Studier and Moffat (Studier & Moffat, 1986). As expected, PtpB appears at a molecular weight of around 31 kDa (Grundner, Ng, & Alber, 2005). However, PtpB is found in insoluble fraction (Figure 3, left).…”

Low Molecular Weight Protein Tyrosine Phosphatases Control Antibiotic Production in Streptomyces coelicolor A3(2)

“…In Actinomycetes (Mycobacterium spp and Streptomyces spp.) despite the presence of tyrosine phosphatases, no tyrosine kinases have been evidenced so far [33]. Classical bacterial tyrosine kinases of the BY-kinase family [10] are absent in Actinomycetes, and it is therefore possible that these bacteria harbor a presently unidentified family of tyrosine kinases or simply possess serine/threonine kinases with relaxed specificity, capable of phosphorylating tyrosine residues.…”