HRBP is a myoactive peptide that excites Aplysia heart and enhances gut motility in vitro. Neurons R3-R14. A cluster of 12 giant neurons located on the right side of the abdominal ganglion. The partial formation of pyroglutamate from N-terminal glutamic acid in peptides isolated from single cells is detected by mass spectrometry (PubMed:9930740). There are indications this modification depends on a heat sensitive factor.