| Primary Identifier | IPR039008 | Type | Domain |
| Short Name | IF_rod_dom |
| description | Intermediate filaments (IF) [, ]are proteins which are primordialcomponents of the cytoskeleton and the nuclear envelope. They generally formfilamentous structures 8 to 14 nm wide. IF proteins are members of a verylarge multigene family of proteins which has been subdivided in six types:Type I: Acidic cytokeratins.Type II: Basic cytokeratins.Type III: Vimentin, desmin, glial fibrillary acidic protein (GFAP),peripherin, and plasticin.Type IV: Neurofilaments L, H and M, alpha-internexin and nestin.Type V: Nuclear lamins A, B1, B2 and C.Type VI: 'Orphan' IF proteins, which are more distant in terms of theiramino acid sequences.All IF proteins are structurally similar in that they consist of: a centralrod domain comprising some 300 to 350 residues which is arranged in coiled-coiled α-helices, with at least two short characteristic interruptions; aN-terminal non-helical domain (head) of variable length; and a C-terminaldomain (tail) which is also non-helical, and which shows extreme lengthvariation between different IF proteins.While IF proteins are evolutionary and structurally related, they have limitedsequence homologies except in several regions of the rod domain. The IF roddomain is approximately 310 residues long in all cytoplasmic IF proteins andclose to 350 residues in the nuclear ones. The IF rod domain exhibits aninterrupted α-helical conformation and reveals apronouncedseven-residue periodicity in the distribution of apolar residues.The heptad periodicity within the rod domain is interrupted in several places,which generates four consecutive α-helical segments: 1A and 1B, whichtogether form the so-called coil 1, and 2A and 2B, which form coil 2. The fourα-helical segments are interconnected by relatively short, variablelinkers L1, L12 and L2 [, ].IF proteins have a very strong tendency to dimerize via the formation of anα-helical coiled coil (CC) by their rod domains []. |
