Keratins, type II
keratins, type ii
These proteins are the most diverse among IFs and constitute type I (acidic) and type II (basic) IF proteins. The many isoforms are divided in two groups:    epithelial keratins (about 20) in epithelial cells (image to right)   trichocytic keratins (about 13) (hair keratins), which make up hair, nails, horns and reptilian scales.   Regardless of the group, keratins are either acidic or basic. Acidic and basic keratins bind each other to form acidic-basic heterodimers and these heterodimers then associate to make a keratin filament.