Test-tube filaments made from genetically engineered human epidermal keratins. On the 
left are filaments from normal keratins; on the right, filaments from keratins with a 
single amino acid substitution (arginine to cysteine). This point mutation was discov- 
ered in a patient with epidermolysis bullosa simplex, a disease involving abnormalities in 
the keratin filament network. 
From Coulombe, P. A., Hutton, M.E., Letai, A., Hebert, A., Paller, A.S., and Fuchs, E. 
1991. Cell 66:1301-131 1. Copyright© 1991 by Cell Press. 
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