Figure 3. Protein structure of K3 and K12, constructed using data from the Human Intermediate Filament Database. Each intermediate filament consists of an N-terminal head domain, a central α-helical rod domain, and a C-terminal tail domain. The rod domain is composed of four helical segments (1A (helix-initiation motif), 1B, 2A, and 2B (helix-termination motif)), which are connected to each other by non-helical linker regions (L1, L12, L2). Variants reported in current (*) and previous studies are depicted in their respective amino acid locations.