MOTS-c

MOTS-c is a 16-amino-acid peptide encoded within the mitochondrial 12S rRNA gene. Its existence is conceptually notable: mitochondrial DNA was long assumed to encode only the respiratory chain subunits and the RNA machinery to translate them, and the mitochondrial-derived peptide class demonstrates that the mitochondrial genome also produces signalling molecules that act on the nucleus. MOTS-c has been shown to translocate to the nucleus under metabolic stress and regulate nuclear gene expression, which puts it in an unusual retrograde-signalling category.

The published mechanistic work involves the folate-methionine cycle, AICAR accumulation and downstream AMPK activation, with research interest in insulin sensitivity and exercise-mimetic phenotypes. It is a straightforward peptide to synthesise and handle; the interest is in what it does, not in getting it into solution.