Structure and biochemistry of mammalian hard keratin.

In this review, the structure and biological formation of hard alpha-keratin are drawn together. The hard keratins comprising wool, hairs, quills, hooves, horns, nails and baleen contain partly alpha-helical polypeptides which show homology with epidermal polypeptides only in the helical regions. These polypeptides (about 32 chains) are organized into intermediate filaments (IFs) of 7.5 nm diameter which are embedded in variable amounts of a matrix of non-helical cystine-rich proteins and glycine-tyrosine-rich proteins. The total number of proteins may exceed 100. In addition keratins contain a variety of lipid components. Wool and hair are produced in follicles in a multistep procedure. In the lower levels of the follicle, IFs without associated matrix are found. Subsequently matrix proteins are laid down between the IFs and further synthesis takes place concurrently. Finally the proteins are insolubilized by the oxidative formation of disulphide bonds. Keratinized fibres shows considerable complexity and diversity in the structural arrangement of IFs and matrix within cortical cells. Typically the IFs show hexagonal packing or give a whorl-like appearance in cross-section.

Wool proteins of New Zealand Romney sheep.

Proteins extracted from the wool of 65 Romney ewes were analysed qualitatively by one- and two-dimensional polyacrylamide gel electrophoresis. Romney wool proteins could be classified into the low-sulfur, high-sulfur, and high-tyrosine protein groups described for wool from other breeds. The wool protein pattern of an individual sheep remained constant despite changes in season, age or nutritional status of the sheep, and did not vary between different body positions. There were between-sheep differences in protein pattern, most variation occurring in the high-sulfur protein group. These differences were presumed to reflect genetic differences between the sheep.