A Search for a Simple Keratin?The Precursor Keratin Proteins From Cow's Lip Epidermis

Abstract

In searching for a material which might contain a homogeneous keratin protein as a major constituent, an examination was made of a soluble keratin precursor from cow's lip epidermis. Formic acid was used as extractant. Assessment of homogeneity was based on behaviour on DEAE-cellulose and on a consideration of the radioactively labelled peptides in a size-charge peptide map of [14C]S-carboxymethylcysteine. containing peptides from an enzyme digest. It is concluded that there is no major homogeneous keratin precursor in cow's lip epidermis and that a family of closely related proteins is present. The situation resembles that found in another a·keratin, wool. There is evidence for the existence of a fraction, amounting to 6-8% of the total protein, of higher sulphur content than the remainder of the protein both in the soluble precursor protein and in the stratum corneum.