Carboxymethyl-phenylalanine as a Replacement for Phosphotyrosine in SH2 Domain Binding

Liang Tong,Thomas C Warren,Susan Lukas,Josephine Schembri-King,Raj Betageri,John R Proudfoot,Scott Jakes

doi:10.1074/jbc.273.32.20238

Liang Tong, Thomas C Warren + Show 5 more

Open Access

https://doi.org/10.1074/jbc.273.32.20238

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Abstract

The crystal structure of human p56(lck) SH2 domain in complex with an inhibitor containing the singly charged p-(carboxymethyl)phenylalanine residue (cmF) as a phosphotyrosine (Tyr(P) or pY) replacement has been determined at 1.8 A resolution. The binding mode of the acetyl-cmF-Glu-Glu-Ile (cmFEEI) inhibitor is very similar to that of the pYEEI inhibitor, confirming that the cmFEEI inhibitor has a similar mechanism of SH2 domain inhibition despite its significantly reduced potency. Observed conformational differences in the side chain of the cmF residue can be interpreted in terms of maintaining similar interactions with the SH2 domain as the Tyr(P) residue. The crystal structure of the free p56(lck) SH2 domain has been determined at 1.9 A resolution and shows an open conformation for the BC loop and an open phosphotyrosine binding pocket, in contrast to earlier studies on the src SH2 domain that showed mostly closed conformation. The structural information presented here suggests that the carboxymethyl-phenylalanine residue may be a viable Tyr(P) replacement and represents an attractive starting point for the design and development of SH2 domain inhibitors with better pharmaceutical profiles.

Highlights

Protein tyrosine phosphorylation is among the first intracellular events in the transduction of many external signals into the cell
We present here the crystal structure of human p56lck src homology 2 (SH2) domain in complex with an inhibitor containing singly charged cmF as the Tyr(P) mimic and show that the cmF residue could be a suitable replacement for Tyr(P)
The crystal structure of the human p56lck SH2 domain in complex with an inhibitor containing a phosphotyrosine replacement has been determined at 1.8 Å resolution

Summary

Introduction

Protein tyrosine phosphorylation is among the first intracellular events in the transduction of many external signals into the cell. Inhibitors containing the phosphotyrosyl residue can become successful therapeutic agents This is due both to the lability of the phosphate group toward hydrolysis and to its doubly negative charge at physiological pH, which significantly reduces cell permeability. The carboxymethyl functionality is an attractive phosphate replacement because it is metabolically stable and contains only a single negative charge. A similar degree of loss in potency was observed when the cmF residue was used as a replacement in an inhibitor against the src SH2 domain [5]. We present here the crystal structure of human p56lck SH2 domain in complex with an inhibitor containing singly charged cmF as the Tyr(P) mimic and show that the cmF residue could be a suitable replacement for Tyr(P)

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