Immunological evidence for two common precursors to corticotropins, endorphins, and melanotropin in the neurointermediate lobe of the toad pituitary.
The biosynthesis of corticotropin (ACTH1--39), beta-endorphin [beta(61--91)-lipotropin] and alpha-melanotropin in the toad intermediate lobe was studied by using immunoprecipitation procedures with antisera specific for these peptides. Intermediate lobes were pulse-incubated with [3H]phenylalanine and then chase-incubated for varying periods; the radioactive proteins were immunoprecipitated. Immunoprecipitates were separated by acidic urea or sodium dodecyl sulfate polyacrylamide gel electrophoresis. Evidence from the pulse-chase and sequential immunoprecipitation studies using antisera to ACTH and beta-endorphin suggests that the toad intermediate lobe synthesizes two common precursors (apparent Mr 32,000 and 29,500) containing both the ACTH and beta-endorphin sequences. These precursors are processed to yield several forms of immunoreactive corticotropin (apparent Mr 23,000, 21,000, 13,000, and 4300), immunoreactive endorphin (apparent Mr 11,700 and 3500), and immunoreactive alpha-melanotropin. The 4300 Mr form of corticotropin and the 11,700 and 3500 Mr forms of endorphins were found to comigrate with synthetic ACTH1--39, beta-lipotropin and beta-endorphin, respectively, on both acidic urea and sodium dodecyl sulfate gels.
D000324:Adrenocorticotropic Hormone / Q000096:biosynthesis* / Q000276:immunology; D000818:Animals; D004723:Endorphins / Q000096:biosynthesis* / Q000276:immunology; D007158:Immunologic Techniques; D009074:Melanocyte-Stimulating Hormones / Q000096:biosynthesis* / Q000276:immunology; D008970:Molecular Weight; D010902:Pituitary Gland / Q000378:metabolism*; D011498:Protein Precursors / Q000276:immunology / Q000378:metabolism*; D014981:Xenopus
D004723:Endorphins; D011498:Protein Precursors; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones