The extraction and characterization of human nail keratin.

We investigated nail keratins obtained by sequential extraction with increasing reducing agent concentrations (50 mM and 200 mM 2-mercaptoethanol) and examined each of the extracted keratins by gel electrophoresis followed by immunoblotting. It was found that nail contained epidermal and hair keratins. With 50 mM 2-mercaptoethanol, only epidermal type of keratins including skin differentiation specific-keratin could be extracted, whereas hair type of keratins required 200 mM 2-mercaptoethanol for extraction from nail. These results may indicate that nail has unique properties with respect to it's keratin compositions. The difference in durabilities of epidermal and hair keratins in nail against 2-mercaptoethanol suggests that two different types of the keratin filaments which are composed of epidermal or hair keratin polypeptides may have differing structural features, despite of co-existence in nail.