title: Chemical synthesis and application of C-terminally 5-carboxyfluorescein-labelled thymopentin as a fluorescent probe for thymopoietin receptor.
abstract: Thymopentin (TP5) is a synthetic pentapeptide fragment, which corresponds to position 32 - 36 of thymic polypeptide thymopoietin. Thymopoietin and TP5 display a variety of biological functions, including phenotypic differentiation of T cells and the regulation of immune systems. Previous chemical modification experiments suggested that there was an absolute requirement for N-terminal amino acids to maintain the biological activity of TP5. On the basis of this structure-activity relationship, we designed and synthesized the C-terminally 5-carboxyfluorescein-coupled TP5 (TP5-FAM) as a fluorescent probe for thymopoietin receptor. TP5-FAM could bind to the membrane of human lymphoid cell lines, MOLT-4 cells, in which the thymopoietin receptor is expressed. The binding is specific and saturable (K(d) = 33 microM). TP5 and human splenopentin are nearly equipotent inhibitors of TP5-FAM binding to the thymopoietin receptor, but porcine secretin did not show any significant inhibition of TP5-FAM binding to MOLT-4 cells. Thus, TP5-FAM is suggested to be a potent and biologically active ligand that would be useful for studying the binding and functional characteristics of the human thymopoietin receptor.
authors.affiliation: Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Toho University, Chiba, Japan. onoue@fureai.or.jp
authors.forename: Satomi
authors.initials: S
authors.lastname: Onoue
authors.forename: Baosheng
authors.initials: B
authors.lastname: Liu
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nemoto
authors.forename: Mariko
authors.initials: M
authors.lastname: Hirose
authors.forename: Takehiko
authors.initials: T
authors.lastname: Yajima
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006801:Humans; D008024:Ligands; D010446:Peptide Fragments / Q000494:pharmacology; D018000:Receptors, Peptide / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000737:chemistry; D012633:Secretin / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013552:Swine; D016305:Thymopentin / Q000737:chemistry / Q000494:pharmacology; D013946:Thymopoietins / Q000494:pharmacology
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; D008024:Ligands; D010446:Peptide Fragments; D018000:Receptors, Peptide; D013946:Thymopoietins; C044349:thymopoietin receptor; D012633:Secretin; C041898:splenopentin; C045132:4-carboxyfluorescein; D016305:Thymopentin