Conserved Site

Intermediate filament protein, conserved site (IPR018039)

Short name: Intermediate_filament_CS


Intermediate filaments (IF) [PMID: 2183847] are proteins which are primordial components of the cytoskeleton and the nuclear envelope. They generally form filamentous structures 8 to 14 nm wide. IF proteins are members of a very large multigene family of proteins, which has been subdivided in five major subgroups:

  • 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.

All IF proteins are structurally similar in that they consist of: a central rod domain comprising some 300 to 350 residues which is arranged in coiled-coiled alpha-helices, with at least two short characteristic interruptions; a N-terminal non-helical domain (head) of variable length; and a C-terminal domain (tail) which is also non-helical, and which shows extreme length variation between different IF proteins. While IF proteins are evolutionary and structurally related, they have limited sequence homologies except in several regions of the rod domain. We use, as a sequence pattern for this class of proteins, a conserved region at the C-terminal extremity of the rod domain.


The PROSITE pattern defining this conserved site is:

[IV] - {K} - [TACI] - Y - [RKH] - {E} - [LM] - L - [DE].

In the third position of the pattern, Ala is found in type IV and V IF proteins, Thr is found in IF proteins of type I, II, III, and VI, Cys in IF from snails, and Ile in IF from worms. In the first position of the pattern Val is found in type VI, Ile is found in all other types.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns