The high sulphur proteins of wool: Towards an understanding of sheep breed diversity

High sulphur proteins (HSPs) form part of the matrix surrounding the intermediate filaments in the cortical cells of the wool fibre. There are three known families of HSPs, comprising in excess of 40 components and their molecular weights range from 10-30 kDa. Here we report the use of the increased resolving power of isoelectric focusing in the first dimension of two-dimensional electrophoresis and modern gel comparison software to investigate the nature of within- and between-breed variations amongst the proteins of three breeds of sheep: Merino, Romney and Corriedale. In agreement with past studies we observed very little variation in the intermediate filament protein content in wool, both between and within these three sheep breeds. Instead, most of the observed variation occurred among the HSPs, along with some minor variation among the high glycine-tyrosine proteins. Breed-specific differences were observed in the HSP patterns in the wool proteome maps. Merino sheep were found to exhibit the simplest HSP expression patterns, with eight major spots linked to form four pairs. In contrast, the Romney and Corriedale HSP patterns exhibited more spots at lower isoelectric point values (around 4.8), while some of the lower molecular weight HSPs were less prevalent in Romney sheep and absent from the Corriedales.