1. Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK
2. Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA
3. Present address: Department of Molecular Pharmacology, Stanford University Medical School, 269 Campus Drive, Stanford University, Stanford, California 94305, USA

Correspondence to: David Barford¹ Correspondence and requests for materials should be addressed to D.B. (Email: david.barford@icr.ac.uk). The coordinates of the sulphenyl-amide and sulphonic acid species of PTP1B have been deposited in the Protein Data Bank under accession codes 1OEM and 1OEO, respectively.

Abstract

The second messenger hydrogen peroxide is required for optimal activation of numerous signal transduction pathways, particularly those mediated by protein tyrosine kinases^{1, 2, 3, 4, 5, 6}. One mechanism by which hydrogen peroxide regulates cellular processes is the transient inhibition of protein tyrosine phosphatases through the reversible oxidization of their catalytic cysteine, which suppresses protein dephosphorylation^{7, 8, 9}. Here we describe a structural analysis of the redox-dependent regulation of protein tyrosine phosphatase 1B (PTP1B), which is reversibly inhibited by oxidation after cells are stimulated with insulin⁸ and epidermal growth factor⁹. The sulphenic acid intermediate produced in response to PTP1B oxidation is rapidly converted into a previously unknown sulphenyl-amide species, in which the sulphur atom of the catalytic cysteine is covalently linked to the main chain nitrogen of an adjacent residue. Oxidation of PTP1B to the sulphenyl-amide form is accompanied by large conformational changes in the catalytic site that inhibit substrate binding. We propose that this unusual protein modification both protects the active-site cysteine residue of PTP1B from irreversible oxidation to sulphonic acid and permits redox regulation of the enzyme by promoting its reversible reduction by thiols.