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Measuring In Vitro ATPase Activity for Enzymatic Characterization
Published on: August 23, 2016
Oxidation state of the active-site cysteine in protein tyrosine phosphatase 1B
Rob L M van Montfort1, Miles Congreve, Dominic Tisi
1Astex Technology Ltd, 436 Cambridge Science Park, Milton Road, Cambridge CB4 0QA, UK.
Nature
|June 13, 2003
Summary
Oxidative stress can irreversibly damage protein tyrosine phosphatase 1B (PTP1B). Researchers discovered a protective sulphenyl-amide intermediate that prevents PTP1B damage and may aid its reactivation.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Protein tyrosine phosphatases (PTPs) regulate critical cell signaling pathways.
- Dysregulation of PTPs is linked to diseases like cancer, diabetes, and hypertension.
- The cellular redox state influences PTP activity via cysteine oxidation, but protective mechanisms against irreversible damage are unknown.
Purpose of the Study:
- To elucidate the structural mechanisms preventing irreversible oxidation of PTP1B's catalytic cysteine.
- To identify protective intermediates in the oxidative inhibition of PTP1B.
- To understand the role of these intermediates in PTP1B regulation and reactivation.
Main Methods:
- X-ray crystallography was used to determine the structures of oxidized PTP1B.
- Identification and characterization of novel oxidized cysteine species in PTP1B.
- Biochemical assays to assess the reversibility of oxidation by glutathione.
Main Results:
- Crystal structures revealed sulphenic, sulphinic, and sulphonic acid forms of PTP1B.
- A novel sulphenyl-amide species, formed by catalytic cysteine oxidation, was identified.
- Formation of the sulphenyl-amide induces significant changes in the PTP1B active site.
- This sulphenyl-amide intermediate is reversible by the cellular reducing agent glutathione.
Conclusions:
- The sulphenyl-amide is a protective intermediate against irreversible oxidative damage to PTP1B.
- This intermediate may play a role in the reactivation of PTP1B by biological thiols.
- The sulphenyl-amide represents a unique regulatory state of PTP1B under oxidative conditions.
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