Download MendeleyConserved N-terminal Regulation of the ACA8 Calcium Pump with Two Calmodulin Binding Sites.
Larsen, S.T., Dannerso, J.K., Nielsen, C.J.F., Poulsen, L.R., Palmgren, M., Nissen, P.(2024) J Mol Biol 436: 168747-168747
- PubMed: 39168442
- DOI: https://doi.org/10.1016/j.jmb.2024.168747
- Primary Citation of Related Structures:
8QMP - PubMed Abstract:
The autoinhibited plasma membrane calcium ATPase ACA8 from A. thaliana has an N-terminal autoinhibitory domain. Binding of calcium-loaded calmodulin at two sites located at residues 42-62 and 74-96 relieves autoinhibition of ACA8 activity. Through activity studies and a yeast complementation assay we investigated wild-type (WT) and N-terminally truncated ACA8 constructs (Δ20, Δ30, Δ35, Δ37, Δ40, Δ74 and Δ100) to explore the role of conserved motifs in the N-terminal segment preceding the calmodulin binding sites. Furthermore, we purified WT, Δ20- and Δ100-ACA8, tested activity in vitro and performed structural studies of purified Δ20-ACA8 stabilized in a lipid nanodisc to explore the mechanism of autoinhibition. We show that an N-terminal segment between residues 20 and 35 including conserved Phe32, upstream of the calmodulin binding sites, is important for autoinhibition and the activation by calmodulin. Cryo-EM structure determination at 3.3 Å resolution of a beryllium fluoride inhibited E2 form, and at low resolution for an E1 state combined with AlphaFold prediction provide a model for autoinhibition, consistent with the mutational studies.
Organizational Affiliation:
Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark; Danish Research Institute of Translational Neuroscience - DANDRITE, Aarhus University, Aarhus, Denmark.
