1H-NMR analysis of CD3-ε reveals the presence of turnhelix structures around the itam motif in an otherwise random coil cytoplasmic tail

Abstract

The conformation adopted in solution by the cytoplasmic tail of CD3-B has been analyzed by 'H-nmr. Tlie cytoplasmic tail is mostly random coil except for the amino acids conforming the imimmoreceptor tyrosine-based activation motif (ITAM), YxxL/IxxxxxxxYxxL. Although the N-terminal YxxL sequence of the motif is poorly folded, adopting 6-residue turn-like conformations with the Tyr side chain in t\vo different orientations, the C-tenninal YxxL sequence is placed in a more complex structure involving a set of nonclassical a-helix turns and -tums that comprises 11 amino acids. Tills st met lire is not modified by phosphorylation of the tyrosine residue. Tlie differences in the conformation adopted around the t\vo tyrosines of the ITAM motif suggest that they may play different roles pertaining to either binding signal transducing proteins or, alternatively, proteins involved in other processes such as endoplasmic reticulum location. ©1997 John Wiley & Sons, Inc.