Alignment of the isomin sequence with other intermediate filaments (IFs) reveals that isomin shares the IF tripartite molecular organization. Sequences reported in figure are representatives of protostome cytoplasmic IFs and lamins. They include: two Caenorhabditis elegans proteins, IFC-1 [Swiss-Prot: O45168] and IFA-1 [Swiss-Prot: P90901]; the non-neuronal IF protein from the mollusc Helix aspersa (IFEA, [Swiss-Prot:P22488]); the IF protein from the annelid Lumbricus terrestris (Lumte, [Swiss-Prot: Q25421]), and lamin Dm0 from Drosophila melanogaster [Swiss-Prot: P08928]. Predicted coiled coil segments forming the central rod domain are shaded in grey. The rod domain is delimited by the conserved helix initiation and helix termination motifs; in the figure, those residues of these signature sequences that are shared by both isomin and at least one of the other IF sequences are evidenced in red. The different coiled coil subdomains within the rod are indicated by horizontal lines. The isomin region still endowed with coiled coil-forming capability that contains most of the helix initiation motif and partly coincides with the beginning of coil 1a in other IFs is boxed in red. The discontinuity in isomin coil 2 that occurs in correspondence of the stutter region of other IFs is marked by an arrowhead. In the lamin sequence, the nuclear signature motif and the terminal CaaX box are evidenced in yellow and in green, respectively; the lamin homology domain, occurring in all the sequences reported in the figure except isomin and IFC-1, is boxed in grey. Symbols underlying the sequence alignment indicate aminoacids that at a given position are identical (*), strongly similar (:) or weakly similar (.).