Letter to the Editor: Complete 1H, 15N and 13C Assignment of a Recombinant Mouse Major Urinary Protein

In the urine of sexually mature male mice there is an ensemble of protein isoforms defined as Major Urinary Proteins (MUP) complex. They belong to the lipocalin superfamily and share with other members of this family the capacity to bind hydrophobic molecules, some of which are odorants. A possible role of the molecules bound by these proteins is territorial marking and/or modulation of behavioural reactions among conspecifics. On the other hand, the proteins as such play an important role in the reproductive cycle of these rodents by acting as pheromones. In fact, MUP, either associated or free of their natural ligands, are able to interact with receptors in the vomeronasal organ of the female mice, priming hormonal and physiological responses. The understanding of the yet unknown mechanisms associated to all these biological functions necessarily requires the knowledge of structural details of these proteins. Because of the difficulty to single out the various wild-type isoforms, we have cloned one of them using the methylotrophic yeast Pichia Pastoris as host. Here, we present the first complete sequence-specific assignment of this recombinant MUP (rMUP: 18707 Da), which provides the basis for elucidating its solution structure and conformational dynamics.