Binding of synthetic LKEKK peptide to human T-lymphocytes

The synthetic peptide LKEKK corresponding to sequence 16-20 of human thymosin-α 1 and 131-135 of human interferon-α 2 was labeled with tritium to specific activity 28 Ci/mol. The [ 3 H]LKEKK bound with high affinity ( K d = 3.7 ± 0.3 nM) to donor blood T-lymphocytes. Treatment of cells with trypsin or proteinase K did not abolish [ 3 H]LKEKK binding, suggesting the non-protein nature of the peptide receptor. The binding was inhibited by thymosin-α 1 , interferon-α 2 , and cholera toxin B subunit ( K i = 2.0 ± 0.3, 2.2 ± 0.2, and 3.6 ± 0.3 nM, respectively). Using [3H]LKEKK, we demonstrated the existence of a non-protein receptor common for thymosin-α 1 , interferon-α 2 , and cholera toxin B-subunit on donor blood T-lymphocytes.