Protein Domain : CH domain superfamily IPR036872

Type	Homologous_superfamily
Description	A number of actin-binding proteins, including spectrin, alpha-actinin and fimbrin, contain a 250 amino acid stretch called the actin binding domain (ABD). The ABD has probably arisen from duplication of a domain which is also found in a single copy in a number of other proteins like calponin or the vav proto-oncogene and has been called calponin homology (CH) domain [, ].A detailed analysis of The CH domain-containing proteins has shown that they can be divided in three groups [ ]:The fimbrin family of monomeric actin cross-linking molecules containing two ABDsDimeric cross-linking proteins (alpha-actinin, beta-spectrin, filamin, etc.) and monomeric F-actin binding proteins (dystrophin, utrophin) each containing one ABDProteins containing only a single amino terminal CH domain. Each single ABD, comprising two CH domains, is able to bind one actin monomer in the filament. The N-terminal CH domain has the intrinsic ability tobind actin, albeit with lower affinity than the complete ABD, whereas the C-terminal CH bind actin extremely weakly or not at all. Nevertheless both CH domains are required for a fully functional ABD; the C-terminal CH domain contributing to the overall stability of the complete ABD throughinter-domain helix-helix interactions [ ]. Some of the proteins containing a single CH domain also bind to actin, although this has not been shown to be via the single CH domain alone []. In addition, the CH domain occurs also in a number of proteins not known to bind actin, a notable example being the vav protooncogene.The resolution of the 3D structure of various CH domains has shown that the conserved core consist of four major α-helices [ ].Proteins containing a calponin domain include:Calponin, which is involved in the regulation of contractility and organisation of the actin cytoskeleton in smooth muscle cells [ ].Beta-spectrin, a major component of a submembrane cytoskeletal network connecting actin filaments to integral plasma membrane proteins [ ].The actin-cross-linking domain of the fimbrin/plastin family of actin filament bundling or cross-linking proteins [ ].Utrophin,a close homologue of dystrophin [ ].Dystrophin, the protein found to be defective in Duchenne muscular dystrophy; this protein contains a tandem repeat of two CH domains [ ].Actin-binding domain of plectin, a large and widely expressed cytolinker protein [ ].The N-terminal microtubule-binding domain of microtubule-associated protein eb1 (end-binding protein), a member of a conserved family of proteins that localise to the plus-ends of microtubules [ ].Ras GTPase-activating-like protein rng2, an IQGAP protein that is essential for the assembly of an actomyosin ring during cytokinesis [ ].Transgelin, which suppresses androgen receptor transactivation [ ].
Short Name	CH_dom_sf