Substrate specificity and inhibitor profile of human recombinant p56lck from a baculovirus expression vector.

p56lck, a member of the src family of non-receptor protein receptor kinases, is required for normal signal transduction through the T cell receptor. Inappropriate T cell activation and proliferation has been identified as an early event in auto-immune disease-agents which control T cell activation through modulation of p56lck kinase activity could therefore be potential therapeutic agents for a range of pathological conditions. To identify p56lck inhibitors, we have established an assay system suitable for the high throughput screening of compound libraries. The assay uses enzyme purified from baculovirus infected SF9 cells, and a novel peptidic substrate identified by L. Cantley from a degenerate combinatorial peptide library. We have used this assay system to screen a number of different compounds as potential inhibitors of p56lck. In addition, peptides based on the substrate sequence were also tested to identify a sequence that could be used in the rational design of peptide inhibitors of p56lck.