Small integral membrane protein (SMIM) 20 is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

that in humans is encoded by the SMIM20

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

. SMIM20 acts as a

prohormone A prohormone is a committed Precursor (chemistry), precursor of a hormone consisting of peptide hormones synthesized together that has a minimal hormonal effect by itself because of its expression-suppressing structure, often created by protein fol ...

to the peptide hormone phoenixin which was discovered for the first time in 2013 in rodent sensory ganglia. In the study of the

evolution of nervous systems The evolution of nervous systems dates back to the first development of nervous systems in animals (or metazoans). Neurons developed as specialized electrical signaling cells in multicellular animals, adapting the mechanism of action potentials ...

, SMIM20 together with

NUCB2 Nucleobindin-2 is a protein that when found in humans is encoded by the ''NUCB2'' gene. Nucleobindin-2 is a calcium-binding EF-hand protein. upplied by OMIMref name="entrez" /> NUCB2 is protein precursor of nesfatin-1 In the study of the evolut ...

have been found to have deep

homology Homology may refer to: Sciences Biology *Homology (biology), any characteristic of biological organisms that is derived from a common ancestor * Sequence homology, biological homology between DNA, RNA, or protein sequences *Homologous chrom ...

across all lineages that preceded creatures with central nervous systems,

bilaterians The Bilateria or bilaterians are animals with bilateral symmetry as an embryo, i.e. having a left and a right side that are mirror images of each other. This also means they have a head and a tail (anterior-posterior axis) as well as a belly an ...

cnidarians Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that th ...

ctenophores Ctenophora (; ctenophore ; ) comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), a ...

, and

sponges Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through ...

as well as in choanoflagellates.

References

Further reading