1.C.89 The Dynorphin Channel-forming Neuropeptide (Dynorphin) Family
Dynorphins, endogeneous opioid peptides, function as ligands to the opioid kappa receptors but also induce non-opioid excitotoxic effects. Dynorphin A can increase the intra-neuronal calcium concentration. Big dynorphin, dynorphin A and to some extent dynorphin A (1-13), but not dynorphin B, allow calcium to enter into large unilamellar phospholipid vesicles with partly negative headgroups (Hugonin et al., 2008). The effects parallel the previously studied potency of dynorphins to translocate through biological membranes and to cause calcein leakage from large unilamellar phospholipid vesicles. No calcium ion influx into vesicles with zwitterionic headgroups was detected (Hugonin et al., 2008).
Dynorphin has a single N-terminal hydrophobic peak, but is otherwise strongly hydrophilic. It shows a region (95aas-165aas) with 36% identity, 51% similarity, and 10% gaps with L-type Ca2+ channel α-subunit (TC#1.A.1.11.2). This may or may not be coincidental. It is homologous throughout much of its length to animal pro-enkephalins which like opiates, are known to stimulate the pleasure centers of the brain.