Proteins and peptides as pheromone signals and chemical signatures

Abstract

Proteins and peptides are used as pheromones by many invertebrates and vertebrates, on land as well as underwater. These molecules are used as pheromones by aquatic animals such as squid, sea hares, and newts. Males in some terrestrial salamander species use high molecular weight glycopeptide pheromones transferred directly to the nostrils of the female. In Drosophila fruit flies, sex peptides in the male's seminal fluid change the female's behaviour so that after mating she rejects other males and starts to lay eggs. The rapid evolution of Drosophila sex peptides and salamander peptide pheromones suggests that sexual conflict may be involved. In mice, exocrine gland-secreting peptide 1 (ESP1) secreted from the male's tear glands is transferred to the female's nose through physical contact during investigation of the facial areas during courtship. ESP1 activates a narrowly specific vomeronasal receptor, leading to receptive behaviour in the female. The urine marks of male territorial house mice contain high concentrations of highly variable major urinary proteins (MUPs). The MUPs bind small molecule pheromones and other odorants, slowly releasing them and thus greatly prolonging the attractive volatile lifetime of the signal. One of the MUPs, darcin, is the same in all male house mice: it is a pheromone in itself. When the female comes into contact with darcin in a scent mark it prompts a learned attraction to both the male's individual chemical signature mixture and the location of the scent mark. Proteins and peptides may also contribute to the highly variable chemical profiles that differ between individual mammals, for example, and that are used as cues to allow individuals to be distinguished.