third calponin homology (CH) domain found in the plastin/fimbrin family
This family includes plastin and fimbrin. Plastin has three isoforms, plastin-1, -2, and -3. Plastin-1, also called intestine-specific plastin, or I-plastin, is an actin-bundling protein in the absence of calcium. Plastin-2, also called L-plastin, or LC64P, or lymphocyte cytosolic protein 1 (LCP-1), is an actin-binding protein that plays a role in the activation of T-cells in response to costimulation through TCR/CD3 and CD2 or CD28. It modulates the cell surface expression of IL2RA/CD25 and CD69. Plastin-3, also called T-plastin, is an actin-bundling protein found in intestinal microvilli, hair cell stereocilia, and fibroblast filopodia. It may play a role in the regulation of bone development. Fimbrin has been found in plants and fungi. Arabidopsis thaliana fimbrin (AtFIM) includes fimbrin-1, -2, -3, -4, and -5, which cross-link actin filaments (F-actin) in a calcium independent manner. They stabilize and prevent F-actin depolymerization mediated by profilin. They act as key regulators of actin cytoarchitecture, probably involved in cell cycle, cell division, cell elongation and cytoplasmic tractus. AtFIM5 is an actin bundling factor that is required for pollen germination and pollen tube growth. Fungal fimbrin binds to actin, and functionally associates with actin structures involved in the development and maintenance of cell polarity. Members of this family contain four copies of the CH domain. This model corresponds to the third CH domain. CH domains are actin filament (F-actin) binding motifs.
Jiyao W et al.(2023). "The conserved domain database in 2023.",