MUP polymorphic variants

Veggerby, C., Payne, C.E., Gaskell, S.J., Robertson, D.H.L., Hurst, J.L. & Beynon, R.J. (2001) Polymorphic variants of mouse majory urinary proteins. . In: Chemical Signals in Vertebrates (Ed. A. Marchlewska-Koj, D. Muller-Schwarze & J. Lepri) pp157-168. Plenum Press, New York.

The major urinary proteins (MUPs) of rodent urine are members of a complex group of proteins that show subtle differences, but which are all likely to have the same overall structure. Because most of the information on MUP variability is derived from inbred laboratory mouse strains, we have undertaken a survey of MUP variants in wild mouse populations. The polymorphic variants and MUP complexity of individual urine samples were assessed analytically by isoelectric focusing on immobilised pH gradients (Payne et al., this volume) and electrospray ionisation mass spectrometry, which yields accurate masses that were compared with predicted masses inferred from cDNA sequences. Individual MUPs were separated by high-resolution ion exchange chromatography and fragmented using restricted specificity proteolytic enzymes. The peptide maps were then analysed by MALDI-TOF mass spectrometry. Comparisons of the peptide maps derived from a series of MUPs allowed us to pinpoint sites of variant sequences, and in some instances, to use peptide mass differences to specify the amino acid substitution. The function of the polymorphic variants is not fully understood, but there is some evidence for a role in the modulation of the kinetics of ligand release (Robertson et al., this volume).