Type I Keratin Sequence

Predicted MW (human): 48 kDa
Observed MW (SDS-PAGE, human): 45 kDa
Isoelectric point (human): 5.7 (Moll et al., 1982)

Distribution: K18 and its preferred partner K8 are expressed in most simple epithelial tissues (e.g., liver, pancreas, kidney, gut epithelial lining, etc.).

Gene cloning and nucleotide sequence

Human:          V. Romano et al., Differentiation 1986
                      R. Leube et al., Differentiation 1986
                      R.G. Oshima et al., J. Biol. Chem. 1986
                      GenBank Accession Number AF179904

Mouse:           P.A. Singer et al., J. Biol. Chem. 1986
                      GenBank Accession Number NM_010664

Predicted amino acid sequence

Null mutation phenotype

Mice carrying a null K18 mutation are viable, fertile, and exhibit a normal
lifespan. Older K18 null mice develop a distinctive liver pathology in which hepatocytes feature K8-positive protein aggregates that resemble Mallory bodies. See Magin et al., J. Cell Biol. 140: 1441-51 (1998) for additional details.

Involvement in human disease

An inherited mutation in keratin 18 has been discovered in a patient with
cryptogenic cirrhosis. Based on the demonstration that this mutation alter keratin filament assembly and the notion that mutant keratin expression can produce liver disease in transgenic mice, it has been proposed by Omary and his colleagues that mutations in K8 or K18 can predispose the liver to develop cryptogenic cirrhosis. See Ku et al., J. Clin. Invest. 99: 19-23 (1997) for details.