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Non-muscle F-actin decorated with non-muscle tropomyosin 1.6
Structural highlights
DiseaseACTB_HUMAN Defects in ACTB are a cause of dystonia juvenile-onset (DYTJ) [MIM:607371. DYTJ is a form of dystonia with juvenile onset. Dystonia is defined by the presence of sustained involuntary muscle contraction, often leading to abnormal postures. DYTJ patients manifest progressive, generalized, dopa-unresponsive dystonia, developmental malformations and sensory hearing loss.[1] Defects in ACTB are the cause of Baraitser-Winter syndrome type 1 (BRWS1) [MIM:243310. A rare developmental disorder characterized by the combination of congenital ptosis, high-arched eyebrows, hypertelorism, ocular colobomata, and a brain malformation consisting of anterior-predominant lissencephaly. Other typical features include postnatal short stature and microcephaly, intellectual disability, seizures, and hearing loss.[2] FunctionACTB_HUMAN Actins are highly conserved proteins that are involved in various types of cell motility and are ubiquitously expressed in all eukaryotic cells. Publication Abstract from PubMedThe actin cytoskeleton is critical for cell migration, morphogenesis, endocytosis, organelle dynamics, and cytokinesis. To support diverse cellular processes, actin filaments form a variety of structures with specific architectures and dynamic properties. Key proteins specifying actin filaments are tropomyosins. Non-muscle cells express several functionally non-redundant tropomyosin isoforms, which differentially control the interactions of other proteins, including myosins and ADF/cofilin, with actin filaments. However, the underlying molecular mechanisms have remained elusive. By determining the cryogenic electron microscopy structures of actin filaments decorated by two functionally distinct non-muscle tropomyosin isoforms, Tpm1.6 and Tpm3.2, we reveal that actin filament conformation remains unaffected upon binding. However, Tpm1.6 and Tpm3.2 follow different paths along the actin filament major groove, providing an explanation for their incapability to co-polymerize on actin filaments. We also elucidate the molecular basis underlying specific roles of Tpm1.6 and Tpm3.2 in myosin II activation and protecting actin filaments from ADF/cofilin-catalyzed severing. Structural basis underlying specific biochemical activities of non-muscle tropomyosin isoforms.,Selvaraj M, Kokate SB, Reggiano G, Kogan K, Kotila T, Kremneva E, DiMaio F, Lappalainen P, Huiskonen JT Cell Rep. 2023 Jan 31;42(1):111900. doi: 10.1016/j.celrep.2022.111900. Epub 2022 , Dec 30. PMID:36586407[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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