The high‐sulfur proteins of α‐Keratins: Their relation to fiber structure and properties

Unrelated keratins, such as horn and fur, have markedly dissimilar physical properties, and these variations can exist, although to a lesser extent, between two non-identical samples of the same keratin. Each keratin examined contains low-sulfur proteins which bear resemblance to each other and this is in accord with the concept that all α-keratins contain microfibrils of similar size and structure. However, these keratins can differ greatly in the type and amount of high-sulfur protein which they contain. It is reasonable then to assume that variations in physical properties between keratins must be due, at least in part, to differences in the proportion or properties of the matrix (high-sulfur protein) which surrounds each microfibril. High-sulfur proteins have been found in every α-keratin examined with horns containing as little as 7% by weight and furs as much as 45% by weight of these proteins. By the supplementary feeding to sheep of cysteine or methionine administered into the abomasum, the high-sulfur protein content of wool can be increased by 50%. This opens the possibility of the control of fiber properties by the dietary manipulation of sheep.