ANALYSIS OF THE SHEEP TRICHOHYALIN GENE - POTENTIAL STRUCTURAL AND CALCIUM-BINDING ROLES OF TRICHOHYALIN IN THE HAIR FOLLICLE

Trichohyalin is a structural protein that is produced and retained in the cells of the inner root sheath and medulla of the hair follicle. T he gene for sheep trichohyalin has been purified and the complete amin o acid sequence of trichohyalin determined in an attempt to increase t he understanding of the structure and function of this protein in the filamentous network of the hardened inner root sheath cells. Sheep tri chohyalin has a molecular weight of 201,172 and is characterized by th e presence of a high proportion of glutamate, arginine, glutamine, and leucine residues, together totaling more than 75% of the amino acids. Over 65% of trichohyalin consists of two sets of tandem peptide repea ts which are based on two different consensus sequences. Trichohyalin is predicted to form an elongated alpha-helical rod structure but does not contain the sequences required for the formation of intermediate filaments. The amino terminus of trichohyalin contains two EF hand cal cium-binding domains indicating that trichohyalin plays more than a st ructural role within the hair follicle. In situ hybridization studies have shown that trichohyalin is expressed in the epithelia of the tong ue, hoof, and rumen as well as in the inner root sheath and medulla of the hair follicle.