A common precursor to two major crab neurosecretory peptides

Abstract

The biosynthesis of proteins by the X-organ sinus gland (XOSG) neurosecretory system of the crab, Cardisoma carnifex was studied using the pulse-chase technique. Analysis of radioactive proteins following 2D-PAGE showed that during pulse incubations of <-30 min a single predominant 14Kd prohormone was synthesized. With chase <-3 hr the primary 14Kd protein was found to undergo differential and/or multiple post-translational modifications prior to its proteolytic cleavage. Increasing the chase to >3 hr showed a shift in labeling from the 14Kd forms to 3 separate 6Kd proteins. Two of the 6Kd proteins were identified as crustacean hyperglycemic peptides (CHH). Similarity in protein labeling using [ 3H]leucine and [ 35S]cysteine suggest a second major peptide group, the H peptide, known to lack cysteine, is also contained within the 14Kd precursor. Peptide mapping of the 14Kd proteins and of unlabeled CHH and peptide H provide substantive evidence for this biosynthetic scheme. Thus, both the CHH and H peptide groups, which together constitute >90% of the XOSG peptide content, in this species, arise from a common 14Kd precursor molecule.