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

• Published in: The Journal of biological chemistry 1998-08, Vol.273 (32), p.20238-20242
• Main Authors: Tong, Liang, Warren, Thomas C., Lukas, Susan, Schembri-King, Josephine, Betageri, Raj, Proudfoot, John R., Jakes, Scott
• Format: Article
• Language: English
• Subjects: Binding Sites - physiology; Crystallography, X-Ray; Enzyme Inhibitors - chemistry; Humans; Lymphocyte Specific Protein Tyrosine Kinase p56(lck) - chemistry; Models, Molecular; Molecular Conformation; Molecular Structure; Phenylalanine - analogs & derivatives; Phosphotyrosine - metabolism; Protein Binding; Protein Conformation; src Homology Domains - genetics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.32.20238

The crystal structure of human p56lck SH2 domain in complex with an inhibitor containing the singly chargedp-(carboxymethyl)phenylalanine residue (cmF) as a phosphotyrosine (Tyr(P) or pY) replacement has been determined at 1.8 Å 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 p56lck SH2 domain has been determined at 1.9 Å resolution and shows an open conformation for the BC loop and an open phosphotyrosine binding pocket, in contrast to earlier studies on the srcSH2 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.