YwIE is a member of the low-molecular-weight protein tyrosine phosphatase (LMW-PTP). It is the only active PAP present in B.subtilis, and PAPs exhibits almost no activity against Protein Serine, Protein Tyrosine, and Protein Threonine peptides. Also, YwIE has been shown to play a role in B.Subtilis's resistance to stress. Elsholz et al. (2012), reported in their paper that protein arginine phosphorylation likely plays a critical physiological and regulatory role in bacteria. They showed that protein arginine phosphorylation is involved in the regulation of homeostasis, biofilm formation, motility, competence, stress, and stringent responses by regulating gene expression and protein activity in Bacillus Subtilis. Their results suggested that the combined action of protein arginine phosphatase and kinase allows for rapid and reversible regulation of protein activity. Also, that protein-arginine-phosphatases reverse the effect of protein arginine kinases (PAKs) in living organisms. In B.Subtilis, YwIE, a PAP, counteracts the action of McsB, a protein arginine kinase (PAK). McsB phosphorylates arginine residues in the winged helix-turn-helix domain of CtsR4, preventing it from binding to DNA, allowing for the expression of the repressed gene. However, YwIE is capable of restoring the DNA-binding ability of the CtsR repressor, a stress response & heat shock regulator in B.Subtilis, by reversing the McsB-mediated phosphorylation4. It accomplishes this by dephosphorylating the CtsR Protein. Additionally, McsB and YwIE are capable of differentiating between phosphoarginine and other amino acid residues