Wikipedia
Humanin is a peptide that is encoded in the mitochondrial genome by the 16S ribosomal RNA gene, MT-RNR2. Its structure contains a three-turn a-helix, and no symmetry.
The length of the peptide depends on where it is produced. If it is produced inside the mitochondria it will be 21 amino acids long. If it is produced outside the mitochondria, in the cytosol, it will be 24 amino acids long. Both peptides have been shown to have biological activity.
Humanin was independently discovered by three labs looking at Alzheimer's disease, apoptosis, and IGF-1 signaling.
Experiments using cultured cells have demonstrated that humanin has both neuroprotective as well as cytoprotective effects and experiments in rodents have found that it has protective effects in Alzheimer's disease models, Huntington's disease models and stroke models (reviewed in ).