Complete amino acid sequence of a mouse epidermal keratin subunit and implications for the structure of intermediate filaments.

We have determined the complete primary structure of an intermediate filament subunit, the 59,000 molecular weight subunit of mouse epidermal keratin, from the nucleotide sequence of cDNA clones. The central portion of the sequence forms extended tracts of a coiled-coil alpha-helical conformation. This is flanked at both termini by similar non-alpha-helical sequences that are extremely rich in glycine residues, frequently configured in tandem peptide repeats. Limited chymotryptic digestion of keratin filaments containing this protein suggests a structural organization whereby the terminal glycine-rich sequences protrude from a conserved core structure into which the coiled-coil alpha-helical segments are packed.