Analysis of the (YXXL/I)2 Signalling Motifs Found in the Cytoplasmic Segment of the Mouse CD3-ζ Chain
The specific recognition of antigen by T cells and its ensuing transduction into intracellular signals is accomplished by the T cell antigen receptor (TCR)-CD3 complex. The transducing subunits of this multimolecular complex, termed CD-3-γ, -δ, -ϵ, -ζ and -η, are noncovalently associated with the antigen binding TCR αβ (or TCR γδ) dimer. They possess large intracytoplasmic segments which are responsible for their signalling properties and made of a recurrent functional domain of ~20 amino acids. Common to each copy of this domain is a pair of Tyr-X-X-Leu/Ile sequences (where X corresponds to a variable residue) separated by seven or eight variable residues. This consensus sequence, hereafter referred to as the (YXXL/I)2 motif, is expressed as a single copy in the cytoplasmic tail of the CD3-δ, CD3-γ and CD3-ϵ subunits.1 The CD3-ζ polypeptide appears to be unique among this set of signalling devices in the sense that it displays three concatenated copies of the (YXXL/I)2 motif (denoted as ζa, ζb, and ζc).2
KeywordsCytoplasmic Tail Cell Antigen Receptor Variable Residue Multimolecular Complex Cytoplasmic Segment
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