The Proteins of Normal and Aberrant Hair Keratins

All mammalian hard keratins consist of filaments about 7 nm in diameter, embedded in a nonfilamentous matrix. Many lines of enquiry have led to the view that the filaments are composed of helical proteins of comparatively low cystine content (low-sulfur proteins) and are responsible for the characteristic a X-ray patterns given by these keratins. The matrix on the other hand is composed of two families of nonhelical proteins, one cystine-rich (high-sulfur proteins: range 18 to 45%), the other rich in glycine and tyrosine (high-tyrosine proteins: range 0 to 20%). In most hairs these three groups of proteins constitute 85% or more of the mass of the fiber; the remainder comprises intercellular membranes, the remnants of cellular constituents, medulla and the enveloping cuticle (Fraser et al., 1972; Bradbury, 1973; Crewther, 1976).