title: Bidirectional binding property of high glycine-tyrosine keratin-associated protein contributes to the mechanical strength and shape of hair.
abstract: Since their first finding in wool 50years ago, keratin-associated proteins (KAPs), which are classified into three groups; high sulfur (HS) KAPs, ultra high sulfur (UHS) KAPs, and high glycine-tyrosine (HGT) KAPs, have been the target of curiosity for scientists due to their characteristic amino acid sequences. While HS and UHS KAPs are known to function in disulfide bond crosslinking, the function of HGT KAPs remains unknown. To clarify the function as well as the binding partners of HGT KAPs, we prepared KAP8.1 and other KAP family proteins, the trichocyte intermediate filament proteins (IFP) K85 and K35, the head domain of K85, and the C subdomain of desmoplakin C-terminus (DPCT-C) and investigated the interactions between them in vitro. Western blot analysis and isothermal titration calorimetry (ITC) indicate that KAP8.1 binds to the head domain of K85, which is helically aligned around the axis of the intermediate filament (IF). From these results and transmission electron microscopy (TEM) observations of bundled filament complex in vitro, we propose that the helical arrangement of IFs found in the orthocortex, which is uniquely distributed on the convex fiber side of the hair, is regulated by KAP8.1. Structure-dependent binding of DPCT-C to trichocyte IFP was confirmed by Western blotting, ITC, and circular dichroism. Moreover, DPCT-C also binds to some HGT KAPs. It is probable that such bidirectional binding property of HGT KAPs contribute to the mechanical robustness of hair.
authors.affiliation: Medical Proteomics Laboratory, Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Matsunaga
authors.affiliation: Medical Proteomics Laboratory, Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Abe
authors.affiliation: Beauty Research, R&D, Kao Corporation, 2-1-3, Bunka, Sumida-ku, Tokyo 131-8501, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ishii
authors.affiliation: Beauty Research, R&D, Kao Corporation, 2-1-3, Bunka, Sumida-ku, Tokyo 131-8501, Japan.
authors.forename: Shun-Ichi
authors.initials: SI
authors.lastname: Watanabe
authors.affiliation: Medical Proteomics Laboratory, Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kiyoshi
authors.affiliation: Beauty Research, R&D, Kao Corporation, 2-1-3, Bunka, Sumida-ku, Tokyo 131-8501, Japan.
authors.forename: Bernd
authors.initials: B
authors.lastname: Nöcker
authors.affiliation: Beauty Research, R&D, Kao Corporation, 2-1-3, Bunka, Sumida-ku, Tokyo 131-8501, Japan. Electronic address: tsuchiya.masaru@kao.co.jp.
authors.forename: Masaru
authors.initials: M
authors.lastname: Tsuchiya
authors.affiliation: Medical Proteomics Laboratory, Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan. Electronic address: tsumoto@ims.u-tokyo.ac.jp.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Tsumoto
mesh_terms: D000595:Amino Acid Sequence; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000378:metabolism; D006197:Hair / Q000737:chemistry*; D006801:Humans; D053564:Keratins, Hair-Specific / Q000737:chemistry / Q000378:metabolism; D053531:Keratins, Type II / Q000737:chemistry / Q000378:metabolism; D055595:Mechanical Phenomena; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D013816:Thermodynamics
chemical_list: D003598:Cytoskeletal Proteins; C507604:KRT85 protein, human; C587173:KRTAP8-1 protein, human; D053564:Keratins, Hair-Specific; D053531:Keratins, Type II
keywords: C subdomain of desmoplakin C-terminus; DPCT-C; Desmoplakin C-terminus; HGT KAP; Helical arrangement; High glycine–tyrosine keratin-associated protein; IF; IFP; ITC; Intermediate filament protein; Isothermal titration calorimetry; ULF; high glycine–tyrosine keratin-associated protein; intermediate filament; intermediate filament protein; isothermal titration calorimetry; unit length filament