Download MendeleyStructure and calcium-binding studies of calmodulin-like domain of human non-muscle alpha-actinin-1.
Drmota Prebil, S., Slapsak, U., Pavsic, M., Ilc, G., Puz, V., de Almeida Ribeiro, E., Anrather, D., Hartl, M., Backman, L., Plavec, J., Lenarcic, B., Djinovic-Carugo, K.(2016) Sci Rep 6: 27383-27383
- PubMed: 27272015
- DOI: https://doi.org/10.1038/srep27383
- Primary Citation of Related Structures:
2N8Y, 2N8Z - PubMed Abstract:
The activity of several cytosolic proteins critically depends on the concentration of calcium ions. One important intracellular calcium-sensing protein is α-actinin-1, the major actin crosslinking protein in focal adhesions and stress fibers. The actin crosslinking activity of α-actinin-1 has been proposed to be negatively regulated by calcium, but the underlying molecular mechanisms are poorly understood. To address this, we determined the first high-resolution NMR structure of its functional calmodulin-like domain (CaMD) in calcium-bound and calcium-free form. These structures reveal that in the absence of calcium, CaMD displays a conformationally flexible ensemble that undergoes a structural change upon calcium binding, leading to limited rotation of the N- and C-terminal lobes around the connecting linker and consequent stabilization of the calcium-loaded structure. Mutagenesis experiments, coupled with mass-spectrometry and isothermal calorimetry data designed to validate the calcium binding stoichiometry and binding site, showed that human non-muscle α-actinin-1 binds a single calcium ion within the N-terminal lobe. Finally, based on our structural data and analogy with other α-actinins, we provide a structural model of regulation of the actin crosslinking activity of α-actinin-1 where calcium induced structural stabilisation causes fastening of the juxtaposed actin binding domain, leading to impaired capacity to crosslink actin.
Organizational Affiliation:
Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia.
