The Origin of Citrulline-Containing Proteins in the Hair Follicle and the Chemical Nature of Trichohyalin, an Intracellular Precursor

This study focused on characterizing the proteins in guinea-pig hair and hair-follicle tissue to understand protein synthesis in hair follicles. Five groups of reduced carboxymethylated proteins were identified, with group 1B proteins being unique to the follicle, likely originating from the medulla and inner-root-sheath layers. Most hair and follicle proteins shared similar properties, but quantitative differences were observed: follicle extracts had more group 2 proteins and fewer group 3 and 4 proteins compared to hair extracts. Additionally, follicle group 4 proteins had more low molecular weight proteins and fewer high molecular weight proteins than hair group 4 proteins. These differences were analyzed in the context of keratin protein synthesis, with group 1B proteins potentially being precursors to mature medulla and inner root sheath proteins.