Developing the wool proteome

The wool proteome has been largely uncharted due to a lack of database coverage, poor protein extractability and dynamic range issues. Yet, investigating correlations between wool physical properties and protein content, or characterising UV-, heat- or processing-induced protein damage requires the availability of an identifiable and identified proteome.In this study we have achieved unprecedented wool proteome identification through a strategy of comprehensive data acquisition, iterative protein identification/validation and concurrent augmentation of the sequence database. Data acquisition comprised a range of different hyphenated MS techniques including LC–MS/MS, LC–MALDI, 2D-LC–MS/MS and SDS-PAGE LC–MS. Using iterative searching of databases and search result combination using ProteinScape, a systematic expansion of identifiable proteins in the sequence database was achieved. This was followed by extensive validation and rationalisation of the protein identifications. In total, 72 complete and 30 partial ovine-specific protein sequences were added to the database, and 113 wool proteins were identified.Enhanced access to ovine-specific protein identification and characterisation will facilitate all wool fibre protein chemistry and proteomics research.     

Unravelling the proteome of wool: towards markers of wool quality traits

With ongoing efforts to make wool more competitive alongside other fibres, notably synthetics, there is a need to obtain a better understanding of the relationship between protein composition and characteristic wool properties to assist sheep breeding programmes. Before this can be achieved, the wool proteome needs to be mapped, by gel and non-gel techniques, and methods developed to reliably quantitate protein expression. Nevertheless, in setting out to achieve this, there are numerous challenges to be faced in the application of proteomics to wool, including the relative lack of wool protein sequence information in the publically accessible databases, the wide variety of proteins in the wool fibre, the high homology within the Type I and Type II keratins, the high degree of homology and polymorphism within individual keratin associated protein families, the dominance of the keratin proteins over others in wool and the peculiar chemistries found in keratins and their associated proteins. This review will discuss the various strategies that have been developed to both identify these proteins in the wool protein map and quantify them with the view to their application to the identification of markers for wool quality traits.     

Proteomic database of wool components

The separation, classification and identification of wool fibre proteins has been of interest for many years. The purposes of this review are to summarise past work in this area and to evaluate the application of modern proteomic techniques to the identification and characterisation of wool proteins. The current state of knowledge of the wool proteome will also be presented.     

Extremozymes for improving wool properties

The project ‘EXTRETEX’ funded by the German Federal Foundation Environment (DBU, Osnabrück, Germany) aims at the improvement of wool properties dyeability, handle, felting behaviour and degree of whiteness by means of enzymes derived from extremophilic micro-organisms. In this paper the effects of a commercial thermo- and alkalistable protease on wool with regard to the degree of whiteness, the dyeability and the felting behaviour are presented. A method to treat wool top and wool fabric was developed on a laboratory scale in which the protease was integrated into the pre-washing step of a dyeing process. This treatment method was than scaled up and tested on an industrial winch beck for fabric. With this method—the addition of enzyme in the pre-washing step—the degree of whiteness is generally enhanced. Dyeing untreated and the enzyme-treated wool with Lanasol Blue 8G leads to an improved dyestuff uptake and a distinctive difference in the colour shade for the latter. Microscopy pictures of fibre cross-sections of these samples display a more even distribution of the dyestuff and a better penetration in the enzyme-treated wool fibres but the colour fastness of the enzyme-treated wool is decreased. Though the felting behaviour of the protease treated wool is significantly improved the felting tendency is still too high for an antifelting finish. An increased damage of the enzyme-treated wool in comparison with the untreated one was not observed.     

Effects of zinc deficiency on the wool growth, skin and wool follicles of pre-ruminant lambs

Two groups of 1-month-old pre-ruminant lambs of similar mean liveweights were fed identical liquid milk-replacer diets except that the zinc contents were either 5 micrograms (deficient diet) or 32 micrograms per gram of dry matter (control diet). These diets were fed for 4 weeks, after which all the lambs received the control diet for 2 weeks. In the lambs fed the deficient diet plasma zinc concentration decreased markedly during the first 2 weeks and skin lesions developed around their mouths. Autophagic vacuoles also developed in most follicle bulbs along with a variety of defects in the wool fibres and progressive inhibition of wool growth. Food intake and liveweight increase were not significantly depressed until the third and fourth weeks of feeding the deficient diet. During this period the wool was shed from the zinc-deficient lambs as a result of the fibres being degraded and distorted within thickened outer root sheaths in the distal (upper) parts of the follicles. In addition, the epidermis of the wool-bearing skin became slightly acanthotic and hyperkeratotic, although not parakeratotic. When the deficient lambs were fed the control diet for 2 weeks, their food intake, liveweight gain and plasma zinc concentration increased to almost those of the control lambs, but their rate of wool growth was still low and the epidermis had not returned to normal. Compared with previous studies the findings of this study suggest that pre-ruminant lambs may be more susceptible to the effects of zinc deficiency than ruminant lambs.     

Growth of wool follicles in culture

Summary A procedure for the culture of isolated wool follicles from Merino sheep is described. Follicles were microdissected from midside skin samples of 2-yr-old wethers and transferred, individually, to 24-well tissue culture plates. When maintained in supplemented Williams’ E medium containing 5 to 10% fetal bovine serum (FBS), insulin, hydrocortisone, and a trace element mixture, fiber growth rates of 40 to 80 μm/day were observed. Follicles maintained their morphologic integrity for up to 7 days, incorporated [methyl-³H]thymidine into DNA and [³⁵S]methionine into intermediate-filament keratins of the growing fiber. Insulin and hydrocortisone stimulated fiber growth at concentrations of 10 μg/ml and 50 ng/ml, respectively, but higher doses were inhibitory. The growth of fibers in response to hydrocortisone and the changes in follicle morphology was similar to those induced in skin after systemic administration of cortisol in vivo. A positive interaction between hydrocortisone and trace elements for follicle survival and hydrocortisone, insulin, and FBS for fiber growth was also found. The successful culture of Merino sheep follicles provides a model with which to study the direct influence of endocrine, nutritional and local factors on wool keratin synthesis independently of systemic shifts in the animals’ metabolism.