trichohyalin (TCHH, THH, THL, TRHY)

^[1]

Function

intermediate filament-associated protein that associates in regular arrays with keratin intermediate filaments of the inner root sheath cells of the hair follicle & the granular layer of the epidermis
later becomes cross-linked to keratin intermediate filaments by isodipeptide bonds
may serve as scaffold protein, together with involucrin, in the organization of the cell envelope or anchor the cell envelope to the keratin intermediate filament network
may be involved in its own Ca+2-dependent postsynthetic processing during terminal differentiation
substrate of transglutaminase
some 200 Arg are probably converted to citrullines by peptidylarginine deimidase
monomer (probable)

consists of 9 domains
domain 1 contains two EF-hand Ca+2-binding domains
domains 2-4, 6, & 8 are almost entirely alpha-helical, configured as a series of peptide repeats of varying regularity, & are thought to form a single-stranded alpha-helical rod stabilized by ionic interactions
domain 6 is the most regular & may bind keratin intermediate filaments directly by ionic interactions
domains 5 & 7 are less well organized & may induce folds in the molecule
domain 9 contains the C-terminus, conserved among different species
belongs to the S100-fused protein family
contains 2 EF-hand domains

found in the hard keratinizing tissues such as the inner root sheath of hair follicles & medulla, & in the filiform papillae of dorsal tongue epithelium (probable)
xpressed during late differentiation of the epidermis