Cross linking proteins such as filamin also exist which bind both MTs and MFs. MFs are also associated with a number of other structures in specific situations, such as the contractile ring in dividing cells, and in specific cell types such as the focal contact in fibroblasts, Figure 6. Distribution of Cytoskeletal Systems in a typical Cell Thin straight lines - Microfilaments. Arranged in bundles in microvilli Wavy thicker black lines - Intermediate Filaments. Summary Microfilaments and Microtubules are similar in many respects, they are polar, dynamic structures whose assembly state is nucleotide dependent and both interact with a host of associated proteins .
IFs are apolar and rather more static polymers which are depolymerised by phosphorylation.
MFs are arranged as gels or bundles in association with a large number of actin binding proteins. MTs are usually single typically have their minus end associated with an MTOC deep within the cell, with the plus end toward the periphery. IFs connect cell-cell junctions to give strength to tissues. All three systems are interconnected to various extents.