| Structural highlights
Function
[PTN1_HUMAN] Tyrosine-protein phosphatase which acts as a regulator of endoplasmic reticulum unfolded protein response. Mediates dephosphorylation of EIF2AK3/PERK; inactivating the protein kinase activity of EIF2AK3/PERK. May play an important role in CKII- and p60c-src-induced signal transduction cascades. May regulate the EFNA5-EPHA3 signaling pathway which modulates cell reorganization and cell-cell repulsion.[1] [2]
Publication Abstract from PubMed
Protein tyrosine phosphatases have diverse substrate specificities and intrinsic activities that lay the foundations for the fine-tuning of a phosphorylation network to precisely regulate cellular signal transduction. All classical PTPs share common catalytic mechanisms, and the important catalytic residues in the first sphere of their active sites have been well characterized. However, little attention has been paid to the second-sphere residues that are potentially important in defining the intrinsic activity and substrate specificity of PTPs. Here, we find that a conserved second-sphere residue, Thr263, located in the surface Q-loop is important for both the function and activity of PTPs. Using PTP1B as a study model, we found that mutations of Thr263 impaired the negative regulation role of PTP1B in insulin signaling. A detailed mechanistic study utilizing steady-state kinetics, Bronsted analysis and pH dependence in the presence of pNPP or phosphopeptide substrates revealed that Thr263 is required for the stabilization of the leaving group during catalysis. Further crystallographic studies and structural comparison revealed that Thr263 regulates the general acid function through modulation of the WPD-loop by the T263:F182/Y/H interaction pair, which is conserved in 26 out of 32 classical PTPs. In addition, the hydrophobic interaction between Thr263 and Arg1159 of the insulin receptor contributes to the substrate specificity of PTP1B. Taken together, our findings demonstrate the general role of the second-sphere residue Thr263 in PTP catalysis. Our findings suggest that the second sphere residues of PTP active site may play important roles in PTP-mediated function in both normal and diseased states.
The second-sphere residue T263 is important for the function and catalytic activity of PTP1B via interaction with the WPD-loop.,Xiao P, Wang X, Wang HM, Fu XL, Cui FA, Yu X, Wen SS, Bi WX, Sun JP Int J Biochem Cell Biol. 2014 Dec;57:84-95. doi: 10.1016/j.biocel.2014.10.004., Epub 2014 Oct 14. PMID:25450460[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Nievergall E, Janes PW, Stegmayer C, Vail ME, Haj FG, Teng SW, Neel BG, Bastiaens PI, Lackmann M. PTP1B regulates Eph receptor function and trafficking. J Cell Biol. 2010 Dec 13;191(6):1189-203. doi: 10.1083/jcb.201005035. Epub 2010, Dec 6. PMID:21135139 doi:10.1083/jcb.201005035
- ↑ Krishnan N, Fu C, Pappin DJ, Tonks NK. H2S-Induced sulfhydration of the phosphatase PTP1B and its role in the endoplasmic reticulum stress response. Sci Signal. 2011 Dec 13;4(203):ra86. doi: 10.1126/scisignal.2002329. PMID:22169477 doi:10.1126/scisignal.2002329
- ↑ Xiao P, Wang X, Wang HM, Fu XL, Cui FA, Yu X, Wen SS, Bi WX, Sun JP. The second-sphere residue T263 is important for the function and catalytic activity of PTP1B via interaction with the WPD-loop. Int J Biochem Cell Biol. 2014 Dec;57:84-95. doi: 10.1016/j.biocel.2014.10.004., Epub 2014 Oct 14. PMID:25450460 doi:http://dx.doi.org/10.1016/j.biocel.2014.10.004
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