Download MendeleyDistinct Ca 2+ -binding thermodynamics reveal a paralogue-specific structural response in the calmodulin-like domain of alpha-actinin-4.
Hocevar, J., Kovacic, M., Plavec, J., Djinovic-Carugo, K., Pavsic, M.(2026) Int J Biol Macromol 384: 154866-154866
- PubMed: 42874945 Search on PubMed
- DOI: https://doi.org/10.1016/j.ijbiomac.2026.154866
- Primary Citation Related Structures:
31DL, 31DM - PubMed Abstract:
The actin cytoskeleton, a complex and dynamic network, is precisely organized into structurally and functionally diverse assemblies by actin-binding proteins. A major group of actin crosslinking proteins are α-actinins. The non-muscle forms, α-actinin-1 and -4, are ubiquitous proteins whose actin crosslinking activity is regulated by Ca 2+ ions. The molecular mechanism of regulation is unknown, but it has been suggested to be driven by structural changes triggered by the binding of Ca 2+ ions to their calmodulin-like domain (CaMD). While the structure and Ca 2+ -binding properties of human α-actinin-1 CaMD have already been investigated, no such data were available for the α-actinin-4 CaMD. To address this, we used structurally informed mutagenesis and isothermal titration calorimetry (ITC) to confirm a homologous single Ca 2+ -binding site in the N-terminal lobe of the α-actinin-4 CaMD. In stark contrast to the α-actinin-1 CaMD, where binding is endothermic, binding to the α-actinin-4 CaMD is exothermic and displays a 6-fold lower affinity towards Ca 2+ . These distinct thermodynamic signatures suggest a paralogue-specific conformational change. Indeed, protein NMR spectroscopy revealed a unique Ca 2+ -induced conformational change of the C-terminal lobe, providing new insights into the molecular mechanisms that modulate α-actinin-mediated actin crosslinking.
- Department of Biochemistry, Faculty of Chemistry and Chemical technology, University of Ljubljana, Ljubljana, Slovenia.
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