Structural consequences of mutations in interfacial Tyr residues of a protein antigen-antibody complex: The case of HyHEL-10-HEL

Mitsunori Shiroishi, Kouhei Tsumoto, Yoshikazu Tanaka, Akiko Yokota, Takeshi Nakanishi, Hidemasa Kondo, Izumi Kumagai

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41 Citations (Scopus)


Tyrosine is an important amino acid in protein-protein interaction hot spots.In particular, many Tyr residues are located in the antigen-binding sites of antibodies and endow high affinity and high specificity to these antibodies. To investigate the role of interfacial Tyr residues in protein-protein interactions, we performed crystallographic studies and thermodynamic analyses of the interaction between hen egg lysozyme (HEL) and the anti-HEL antibody HyHEL-10 Fv fragment. HyHEL-10 has six Tyr residues in its antigen-binding site, which were systematically mutated to Phe and Ala using site-directed mutagenesis. The crystal structures revealed several critical roles for these Tyr residues in the interaction between HEL and HyHEL-10 as follows: 1) the aromatic ring of Tyr-50 in the light chain (LTyr-50) was important for the correct ternary structure of variable regions of the immunoglobulin light chain and heavy chain and of HEL; 2) deletion of the hydroxyl group of Tyr-50 in the heavy chain (HTyr-50) resulted in structural changes in the antigen-antibody interface; and 3) the side chains of HTyr-33 and HTyr-53 may help induce fitting of the antibody to the antigen. Hot spot Tyr residues may contribute to the high affinity and high specificity of the antigen-antibody interaction through a diverse set of structural and thermodynamic interactions.

Original languageEnglish
Pages (from-to)6783-6791
Number of pages9
JournalJournal of Biological Chemistry
Issue number9
Publication statusPublished - Mar 2 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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