RL-37 is an antimicrobial peptide and was found in the Rhesus monkey.
Macaque and leaf-eating monkey RL-37 peptides, like other helical antimicrobial peptides found in insect, frog, and mammalian species, were unstructured in bulk solution and had a potent, salt and medium independent antimicrobial activity in vitro, which may be the principal function also in vivo. Human LL-37 and the orangutan, hylobates, and callithrix homologues instead showed a salt-dependent structuring and likely aggregation in bulk solution that affected antimicrobial activity and its medium dependence. The two types of peptides differ also in their interaction with host cells. The evolution of these peptides has thus resulted in distinct mechanisms of action that affect the direct antimicrobial activity andmayalso modulate accessory antimicrobial functions due to interactions with host cells.