Molecular mechanisms underlying the neuroendocrine occurrence, biosynthesis, molecular characteristics and function of neuroendocrine peptides and proteins are being studied, with emphasis on the neuropeptide hormones oxytocin and vasopressin, associated neurophysins (NP's), and their biosynthetic precursors. An hypothesis has been examined that biosynthetic precursors of the neurohypophysial hormones adopt a defined conformational organization upon completion of translation and that this organization helps regulate the production of active peptides produced in neuroendocrine pathways which make the precursors. Chemical methods have been devised to produce biosynthetic precursors and both sequence-designed and site-specific mutants. These methods have been used to prepare semisynthetic oxytocin/neurophysin I and Arg 8 vasopressin/neurophysin II precursor analogs. Evaluation of structural characteristics of the semisynthetic precursors shows that the precursors are well- ordered, folded molecules which can form self-associated species. The latter are concluded to be the prevailing forms in neurosecretory granules in which enzymatic processing occurs. Evaluation of the impact of these characteristics on enyzmatic processing has been made by comparing rates and products of processing of intact precursors to these properties for synthetic fragments containing processing sites. Separately, evaluation has been extended of the relationship between occurrence of the hormone/NP neuroendocrine system in the ovary versus that in hypothalamo-neurophysial system. The relationships of ovarian molecular species to those produced in the hypothalamo- neurohypophysial pathway are being studied. In addition to neurophysin and oxytocin, a newly identified neurophysin-binding species has been found in both sites and is currently being characterized. The data obtained in this study are being used to help define the relationship between molecular mechanisms which occur in different neuroendocrine sites.
