Structural nature of the interaction between T lymphocyte surface molecule CD4 and the intracellular protein tyrosine kinase Ick

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Abstract
The strong non‐covalent interactions between T lymphocyte surface CD4 or CD8 molecules and the intracellular membrane‐associated protein tyrosine kinase Ick are likely to mediate the role of CD4 and CD8 molecules in the immune response. The delineation of the structural nature of the CD4/Ick and CD8/Ick complexes is important for the understanding of the biochemical and functional significance of the interactions. Complementary charged regions in the C‐terminal intracyto‐plasmic portions of CD4 or CD8, and in the N‐terminal region of protein tyrosine kinase Ick were noted. Peptides spanning these regions, residues 417 to 429 of CD4 and 10 to 22 of Ick, were found to specifically dissociate these two molecules in CD4/Ick complexes. A structural model of the interaction that accounts for its high stability is proposed.