title: Proteolytic processing of egg-laying hormone-related precursors in Aplysia. Identification of peptide regions critical for biological activity.
abstract: The atrial gland of the marine mollusk Aplysia californica is an exocrine organ that expresses at least three genes belonging to the egg-laying hormone (ELH) family. In order to study the post-translational processing of the ELH-related gene products in the atrial gland and how it compares to the bag cells, peptides were isolated from the atrial gland and chemically characterized. The A- and B-related precursors were each cleaved in vivo to yield several major and minor peptides including peptides A and B and the ELH-related peptide complexes that caused egg laying. About 13% of the peptide complexes were further enzymically processed by the atrial gland to yield smaller fragments, which included A-AP.A-ELH-(15-36), A-AP.[Ala27]A-ELH-(15-36), and A-AP.[Gln23,Ala27]A-ELH-(16-36), where A-AP is an acidic peptide encoded by the A- and B-related genes and A-ELH is an ELH-related peptide encoded by the A gene. These processed peptide fragments were not active in an egg-laying bioassay, indicating that retention of the 14-residue NH2-terminal segment of the A-ELH-related sequence, or some portion thereof, was critical for the induction of egg laying. Other characterized peptides included two novel 13-residue NH2-terminal peptides, A-NTP and B-NTP, representing residues 22-34 of the A and B precursors, respectively. These two peptides occurred adjacent to the signal peptide region in each precursor, and their characterization established the site of signal peptide cleavage to be the Ser21-Gln22 peptide bond of each precursor. Intermediate peptide fragments (A-NTP-peptide A and B-NTP-peptide B) were also identified indicating that there was a specific ordering in the cleavage of peptide bonds during posttranslational processing. Finally, a new 55-residue atrial gland peptide was also isolated that was not a part of any ELH-related precursor characterized to date.
authors: Marine Biomedical Institute, University of Texas Medical Branch, Galveston 77550.
authors: G T
authors: GT
authors: Nagle
authors: S D
authors: SD
authors: Painter
authors: J E
authors: JE
authors: Blankenship
authors: A
authors: A
authors: Kurosky
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D005260:Female; D007447:Invertebrate Hormones / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational
chemical_list: D000596:Amino Acids; D007447:Invertebrate Hormones; D011498:Protein Precursors; C026880:egg-laying hormone, Mollusca