A predicted alpha-helix mediates targeting of the proprotein convertase PC1 to the regulated secretory pathway

The proprotein convertase PC1 is a protease whose activity is largely confi ned to the dense core secretory granules of neuroendocrine cells. Efficient processing of PC1 substrates in granules requires a mechanism that will bo th limit the activity of the enzyme to these organelles and promote its tar geting to the nascent secretory granules. In the current study, we provide evidence that targeting of PC1 to secretory granules is mediated by alpha - helical structures in its C-terminal tail and, at least in part, is depende nt on interactions with specific components of the secretory granule membra ne.