Calcium causes stiff joints in ɑ-actinin

3D-print of the molecular structure of calcium regulated E. histolytica α-actinin dimer. Calmodulin like domains in blue and violet, actin binding domain in red, spectrin-like repeats in green and connecting “neck” region in yellow. (c) Max Perutz Labs

3D-print of the molecular structure of calcium regulated E. histolytica α-actinin dimer. Calmodulin like domains in blue and violet, actin binding domain in red, spectrin-like repeats in green and connecting “neck” region in yellow. (c) Max Perutz Labs

The group of Kristina Djinovic-Carugo has revealed the molecular structure of a calcium-regulated form of the protein α-actinin, and has elucidated the mechanism of how calcium binds and regulates it. In α-actinin from the parasite E. histolytica, calcium binding triggers an increase in protein rigidity, which impairs its ability to bundle actin filaments. The study is published in PNAS and could help understand calcium regulation in human forms of α-actinin. The mechanism may also provide guidance for the development of novel therapeutics to treat amoebic dysentery caused by E. histolytica that threatens millions of people in developing countries every year.

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