Onset of neurophysin self-association upon neurophysin/neuropeptide hormone precursor biosynthesis

The potential of the common biosynthetic precursor of neurophysin and neuropeptide hormones to self-associate has been assessed by quantitative affinity chromatographic analysis. The precursor form, with the hormone sequence in the amino terminal region and assumed able to interact intramolecularly with the hormone binding site of the neurophysin domain of the folded precursor, exhibits an affinity for neurophysin-agarose which is intermediate between those of unliganded neurophysin and non-covalently hormone-liganded neurophysin. The results lead to a prediction that neurophysin self-association is established upon precursor synthesis and prior to limited proteolysis of the precursor to release mature neurophysin and hormone components. Such self-association could play a role in packaging of the precursor into secretory granules and in regulating subsequent precursor processing events within the granules.