Two-dimensional electrophoretic analysis of human hair keratins, especially hair matrix proteins

Human hair keratins are composed of hair fibrous proteins (HFP) forming 10-nm filaments and nonfilamentous cysteine-rich hair matrix proteins (HMP); these proteins are highly cross-linked by disulfide bonds. In order to obtain high-resultional separation of HFP and HMP by two-dimensional polyacrylamide gel electrophoresis according to isoelectric point (IP) in the first dimension and molecular weight (MW) in the second dimension, these proteins were converted to S-carbamoylmethylated (SCam) derivatives with nonionizable iodoacetamide; this treatment hardly modified the electrophoretic mobility. SCam-HFP were separated into polypeptides with MW 41.5-59 kD (IP pH 5.1-6.8). SCam-HMP were subdivided into two groups; 14 polypeptides of acidic HMP with MW 15-28 kD (IP pH 5.0-7.0) and 12 polypeptides of basic HMP with MW 18.5-28 kD (IP pH 7.8-8.8). Variation in electrophoretic patterns among hair samples obtained from 15 persons in four Japanese families was found in acidic HMP, but not in HFP in basic HMP. The present method appears to be very suitable for the biochemical analysis of human hair keratins, especially HMP of nonfilamentous proteins.