Structure-Function Analyses of a Keratin Heterotypic Complex Identify Specific Keratin Regions Involved in Intermediate Filament Assembly

• Published in: Structure (London) 2020-03, Vol.28 (3), p.355-362.e4
• Main Authors: Lee, Chang-Hun, Kim, Min-Sung, Li, Shuang, Leahy, Daniel J., Coulombe, Pierre A.
• Format: Article
• Language: English
• Subjects: 2B domain; Animals; crystal structure; Crystallography, X-Ray; cytoskeleton; epidermolysis bullosa simplex; epithelium; Humans; intermediate filament; Intermediate Filaments - metabolism; Keratin-14 - chemistry; Keratin-14 - genetics; Keratin-14 - metabolism; Keratin-5 - chemistry; Keratin-5 - genetics; Keratin-5 - metabolism; keratinocyte; Mice; Models, Molecular; Mutagenesis, Site-Directed; Mutation; NIH 3T3 Cells; Protein Domains; Protein Multimerization; Protein Structure, Secondary; self-assembly; skin; structural protein
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2020.01.002

Intermediate filaments (IFs) provide vital mechanical support in a broad array of cell types. Interference with this role causes cell fragility and accounts for a large number of human diseases. Gaining an understanding of the structure of IFs is paramount to understanding their function and designing therapeutic agents for relevant diseases. Here, we report the 2.6-Å resolution crystal structure of a complex of interacting 2B domains of keratin 5 (K5) and K14. K5 and K14 form a long-range, left-handed coiled coil, with participating α helices aligned in parallel and in register. Follow-up mutagenesis revealed that specific contacts between interacting 2B domains play a crucial role during 10-nm IF assembly, likely at the step of octamer-octamer association. The resulting structural model represents an atomic-resolution visualization of 2B-2B interactions important to filament assembly and provides insight into the defects introduced by mutations in IF genes associated with human skin diseases. [Display omitted] •We report on the crystal structure of 2B domain heterocomplexes of K5 and K14•Proper alignment between 2B domains is key to intermediate filament assembly•Our coil 2 model provides detailed understanding of intermediate filament structure•The proposed model helps elucidate how mutations in keratins cause human disease Our understanding of the assembly and structure of 10-nm keratin intermediate filaments remains superficial. Here, Lee et al. report on the crystal structure of 2B domain heterocomplexes from keratin 5 and keratin 14. Mutagenesis studies highlight 2B-2B molecular interactions that are poised to sustain filament elongation during polymerization.