Calponin homology domain <p>The calponin homology domain (also known as CH-domain) is a superfamily of actin-binding domains found in both cytoskeletal proteins and signal transduction proteins [<cite idref="PUB00001696"/>]. It comprises the following groups of actin-binding domains:<ul><li>Actinin-type (including spectrin, fimbrin, ABP-280) (see <db_xref db="INTERPRO" dbkey="IPR001589"/>).</li><li>Calponin-type (see <db_xref db="INTERPRO" dbkey="IPR000557"/>).</li></ul> </p><p>A comprehensive review of proteins containing this type of actin-binding domains is given in [<cite idref="PUB00004975"/>].</p><p>The CH domain is involved in actin binding in some members of the family. However in calponins there is evidence that the CH domain is not involved in its actin binding activity [<cite idref="PUB00003095"/>]. Most proteins have two copies of the CH domain, however some proteins such as calponin and the human vav proto-oncogene (<db_xref db="SWISSPROT" dbkey="P15498"/>) have only a single copy. The structure of an example CH-domain has recently been solved [<cite idref="PUB00003938"/>].</p><p>This entry represents the calponin-homology (CH) domain, a superfamily of actin-binding domains found in cytoskeletal proteins (contain two CH domain in tandem repeat), in regulatory proteins from muscle, and in signal transduction proteins. This domain has a core structure consisting of a 4-helical bundle. This domain is found in:</p><p> <ul><li>Calponin, which is involved in the regulation of contractility and organisation of the actin cytoskeleton in smooth muscle cells [<cite idref="PUB00025538"/>].</li><li>Beta-spectrin, a major component of a submembrane cytoskeletal network connecting actin filaments to integral plasma membrane proteins [<cite idref="PUB00042610"/>].</li><li>The actin-cross-linking domain of the fimbrin/plastin family of actin filament bundling or cross-linking proteins [<cite idref="PUB00036320"/>].</li><li>Utrophin,a close homologue of dystrophin [<cite idref="PUB00018082"/>].</li><li>Dystrophin, the protein found to be defective in Duchenne muscular dystrophy; this protein contains a tandem repeat of two CH domains [<cite idref="PUB00024350"/>].</li><li>Actin-binding domain of plectin, a large and widely expressed cytolinker protein [<cite idref="PUB00031059"/>].</li><li>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 [<cite idref="PUB00029793"/>].</li><li>Ras GTPase-activating-like protein rng2, an IQGAP protein that is essential for the assembly of an actomyosin ring during cytokinesis [<cite idref="PUB00029697"/>].</li><li>Transgelin, which suppresses androgen receptor transactivation [<cite idref="PUB00042611"/>].</li></ul> </p>