Fimbrin belongs to the calponin homology (CH) domain superfamily of actin cross-linking proteins.

Like other members of this superfamily, which include α-actinin, β-spectrin, dystrophin, ABP-120 and filamin, it has a conserved 27 kDa actin-binding domain that contains a tandem duplication of a sequence that is homologous to calponin.

[6] In humans, three highly homologous, strictly tissue and locale specific isoforms have been identified: I-, T- and L-fimbrin.

[6] Owing to the close proximity of its tandem actin-binding domains, fimbrin directs the formation of tightly bundled actin filaments that participate in dynamic processes, including cytokinesis in yeast and host cell invasion by enteropathic bacteria.

Although fimbrin's involvement in processes like these as well as its role in assembly and regulation of microfilament networks are well documented, there are fewer experimental data describing the overall domain organization of the molecule.