Synthetic Fragments of the CD4 Receptor Cytoplasmic Domain and Large PolycationsAlter the Activities of the pp56(lck) Tyrosine Protein Kinase

摘要

In CD4+ T cells, the src-like tyrosine kinase pp56 is associated with the CD4receptor and cross-linking of CD4 results in the activation of this enzyme. The mechanism responsible for this activation is not known, although there is evidence that the activities of the src family of enzymes are regulated by tyrosine phosphorylation. Here we report that pp56-catalyzed angiotensin II phosphorylations are activated 20-fold in vitro by synthetic peptides reproducing portions of the murine CD4 cytoplasmic domain. This activation is described by a dissociation constant of about 2 micrometers.