Question

Why is it significant that arginine vasopressin is expressed in squirrel monkeys and the amino acid sequence is identical to humans?

Answer 1

Oxytocin is widely believed to be present and structurally identical in all placental mammals.Now it has been report that multiple species of New World monkeys possess a novel form of oxytocin,P8 oxytocin. This mutation arises from a substitution of a leucine to a proline in amino acid position 8. Further analysis of this mutation in Saimiri sciureus (squirrel monkey) indicates that [P8] oxytocin is transcribed and translated properly. This mutation is specific to oxytocin, as the peptide sequence for arginine vasopressin, a structurally related nonapeptide, is unaltered. These findings dispel the notion that all placental mammals possess a ‘universal’ oxytocin sequence, and highlight the need for research on the functional significance of this novel nonapeptide in New World monkeys.

Oxytocin is a cyclic nonapeptide hormone with a wide spectrum of reproductive and social effects in mammals, ranging from uterine contractions and lactation to affiliative behaviour and parenting . With the exception of cartilaginous fishes, the amino acid sequence of oxytocin in vertebrates is highly conserved, with relatively few changes over the course of 400 Myr . The amino acid sequence of oxytocin (CYIQNCPLG) is identical in all placental mammals examined to date, suggesting a strong selective pressure to withstand sequence variation . However,The evolutionary lineage of oxytocin can be traced to isotocin ([S4,I8]-oxytocin), which is found in different classes of bony fishes (e.g. Neopterygii, Crossopterygii). Isotocin is the predecessor to mesotocin p8-oxytocin), found in lungfishes, amphibians, reptiles, birds and most marsupials. Oxytocin evolved with the emergence of eutherian mammals (placental mammals) . we demonstrate herein that multiple New World monkey species possess a position-8 amino acid substitution in the oxytocin peptide a leucine to a proline