The term keratin protein covers a class of proteins which includes intermediate filament proteins (IFPs) and intermediate filament associated proteins (IFAPs) that are known to occur in nature in a variety of different cell types [1]. The IFPs are so named because they have been found to be associated in intermediate filaments (IFs), a class of intracellular filamentous structures that are intermediate in size between microtubules and microfilaments. The IFPs have been found to occur in both the nuclei and cytoplasm of almost all differentiated eukaryotic cells, including epithelial, neuronal and glial cells, in addition to the cells of hair fibres, horns and nails. At least five types of IFPs are known. The acidic Type I and neutral-basic Type II chains are found in the hard α-keratins, such as in wool and hair fibres, and keratin in filaments composed of keratin-like proteins (cytokeratins) in epithelial cells. Type III chains occur in cells of mesenchymal origin, in smooth, cardiac and skeletal myogenic cells, glial cells and astrocytes and neuronal cells; Type IV chains are found solely in neuronal cells; and Type V chains are found within the nuclear envelope of mammalian cells