Pheromone binding to two rodent urinary proteins revealed by X-ray crystallography

Abstract

The principal protein excreted in male rat urine, urinary alpha 2-globulin and the homologous mouse protein, major urinary protein, have been well characterized, although their functions remain unclear. Male rat urine affects the behaviour and sexual response of female rats, leading to the proposal that rodent urinary proteins are responsible for binding pheromones and their subsequent release from drying urine. Urinary alpha 2-globulin is also involved in hyaline droplet nephropathy, an important toxicological syndrome in male rats resulting from exposure to a number of industrial chemicals and characterized by the accumulation of liganded urinary alpha 2-globulin in lysosomes in the kidney, followed by the induction of renal cancer. We now report the three-dimensional structures of mouse major urinary protein (at 2.4 A resolution) and rat urinary alpha 2-globulin (at 2.8 A resolution). The results corroborate the role of these proteins in pheromone transport and elaborate the structural basis of ligand binding.

The lipocalin protein family: structure and function

“…standing of how the family has evolved, suggesting that it is very much older and more widespread than has been supposed. In contrast with their low conservation at the sequence level, analysis of available lipocalin crystal structures, which include plasma retinol-binding protein (RBP) [11], β-lactoglobulin (Blg) [12], insecticyanin [13], bilin-binding protein (BBP) [14,15], major urinary protein (MUP) and α #u -globulin [16], odorant-binding protein (OBP) [17] and epididymal retinoic acid-binding protein [18], shows that the overall folding pattern common to the lipocalins is highly conserved. The nature of this common structure is now well described (see Figures 1 and 2) [2,11].…”

“…There is increasing evidence, from a wide variety of different tissues, that RBP binding to its target cells occurs via specific surface receptors [27,28]. A cell-surface receptor for α " -microglobulin (A1M) has also been identified [29,30], and there is additional evidence to suggest the existence of receptors for MUP [16], Blg [12,31], and OBP [32]. Epidydimal secretory protein has been shown to bind to the plasma membrane of spermatozoa [33], and may be another lipocalin to act via a specific surface receptor.…”

The lipocalin XLCpl1 expressed in the neural plate of Xenopus laevis embryos is a secreted retinaldehyde binding protein

“…Likewise, retinoids are required for processes such as vision, reproduction, and hematopoiesis. Furthermore, due to a powerful growth inhibitory effect on a (Bocskei et al, 1992), lepa-A (Newcomer, 1993), and lbbp-D (Huber et al, 1987). Extended regions and the helix were presented in different colors: El, green; E2, brown; E3-4, cyan, E5, blue; E6-7, red; E8, magenta; H1, yellow.…”

High resolution X‐ray structures of mouse major urinary protein nasal isoform in complex with pheromones

“…20 Interestingly, SBT binds to MUP-IV about 20 times more tightly than to any of the five most abundant group 1 isoforms. 20 The first X-ray crystal structure of MUP 21 confirmed that the mouse MUP belong to the lipocalin superfamily. 22 X-ray and NMR structures of MUP-I and MUP-II have been determined in the presence of SBT 23,24 as well as other ligands.…”

“…This is consistent with the findings of other groups, where significant difference electron density peaks are observed in the MUP binding pocket even in the absence of exogenously introduced ligand. 21,24,26 Data collection and refinement statistics are presented in Table I.…”