Intermediate filaments
intermediate filaments
Intermediate filaments (IF) are proteins which are primordial components of the cytoskeleton and the nuclear envelope. They generally form filamentous structures 8 to 14 nm wide and intermediate in size between microtubules and microfilaments. This family of protein includes cytokeratins, vimentin, desmin, glial fibrillary acidic protein, neurofilament proteins and nestin. All IF proteins are structurally similar in that they consist of: a central rod domain which is arranged in coiled-coiled alpha-helices, with at least two short characteristic interruptions; an N-terminal non-helical domain (head) of variable length; and an C-terminal domain (tail) which is also non-helical and shows extreme length variation between different IF proteins.