Neuroendocrine protein of the granin family that regulates the biogenesis of secretory granules. Interacts with Secretogranin III/SCG3. Neuroendocrine and endocrine secretory granules. Brain. Expression in the pituitary is restricted to the anterior lobe. Expression in the hypothalamus is observed in the neuronal cells and neurons of arcuate nucleus, supraoptic nucleus and median eminence (at protein level). Binds calcium with a low-affinity. Belongs to the chromogranin/secretogranin protein family.