title: Forms of immunoreactive beta-endorphin in the intermediate pituitary of the holostean fish, Amia calva.
abstract: Acid extracts of the intermediate pituitary of the holostean fish, Amia calva, were fractionated by gel filtration chromatography and analyzed with radioimmunoassays specific for N-acetylated beta-endorphin and C-terminally amidated alpha-MSH. In these extracts beta-endorphin-related immunoreactive material and alpha-MSH-related immunoreactive material were present in roughly equimolar amounts. The immunoreactive beta-endorphin-sized material was tested for opiate receptor binding activity using a beta-endorphin radioreceptor assay. The results of these studies were negative. The immunoreactive beta-endorphin-sized material was further analyzed by cation exchange chromatography at pH 2.5. Two major and three minor peaks of immunoreactive material were isolated. Peak 5 exhibited a net charge of +7 at pH 2.5 and represented 53% of the total immunoreactivity recovered. Peak 2 with a net charge of +3 at this pH represented 38% of the total immunoreactivity recovered. The minor forms, Peaks 1, 3 and 4, exhibited net charges of +2, +4 and +6, respectively. The apparent molecular weights of Peaks 2 and 5 were determined on a Sephadex G-50 column. Peak 2 had an apparent molecular weight of 2.7 Kd and Peak 5 had an apparent molecular weight of 3.5 Kd. Reverse phase HPLC analysis of Peak 5 indicates that this form of Amia beta-endorphin had chromatographic properties similar to salmon beta-endorphin II. These results would suggest that N-terminal acetylation and C-terminal proteolytic cleavage are important post-translational modifications of the forms of Amia beta-endorphin.
authors.affiliation: University of Denver, Department of Biological Sciences, CO 80208.
authors.forename: R M
authors.initials: RM
authors.lastname: Dores
authors.forename: C A
authors.initials: CA
authors.lastname: Sei
authors.forename: M A
authors.initials: MA
authors.lastname: Morrissey
authors.forename: J W
authors.initials: JW
authors.lastname: Crim
authors.forename: H
authors.initials: H
authors.lastname: Kawauchi
mesh_terms: D000107:Acetylation; D000818:Animals; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D003429:Cross Reactions; D005260:Female; D005399:Fishes / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008970:Molecular Weight; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011863:Radioimmunoassay; D001615:beta-Endorphin / Q000276:immunology / Q000378:metabolism*
chemical_list: D001615:beta-Endorphin