title: Cooperativity of thymopoietin 32-36 (the active site) and thymopoietin 38-45 in receptor binding.
abstract: Thymopoietin is a 49 amino acid polypeptide hormone of the thymus whose biological activity is reproduced by the synthetic pentapeptide thymopentin, corresponding to amino acids 32-36. Thymopentin requires the addition of an octapeptide corresponding to thymopoietin 38-45 for full competition with native thymopoietin in a radioreceptor assay with receptor derived from the human T-cell line CEM. Thus thymopoietin appears to bind to its receptor on T-cells by two regions (32-36 and 38-45). Thymopentin alone is biologically active and induces elevations of intracellular cyclic GMP. Whilst occupancy of the adjacent site by thymopoietin 37-45 does not of itself cause an elevation of intracellular cyclic GMP this peptide is not biologically silent as it does enhance the potency of thymopentin.
mesh_terms: D000595:Amino Acid Sequence; D001667:Binding, Competitive; D002460:Cell Line; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D007945:Leukemia, Lymphoid / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018000:Receptors, Peptide; D013601:T-Lymphocytes / Q000378:metabolism; D016305:Thymopentin; D013946:Thymopoietins / Q000378:metabolism*; D013951:Thymus Hormones / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; D013946:Thymopoietins; D013951:Thymus Hormones; C044349:thymopoietin receptor; C044344:thymopoietin (38-45); D016305:Thymopentin