Calmodulin-like (CML) proteins are major EF-hand-containing, calcium (Ca2+)-binding proteins with crucial roles in plant development and in coordinating plant stress tolerance. Given their abundance in plants, the properties of Ca2+ sensors and identification of novel target proteins of CMLs deserve special attention. To this end, we recombinantly produced and biochemically characterized CML36 from Arabidopsis thaliana. We analyzed Ca2+ and Mg2+ binding to the individual EF-hands, observed metal-induced conformational changes, and identified a physiologically relevant target. CML36 possesses two high-affinity Ca2+/Mg2+ mixed binding sites and two low-affinity Ca2+-specific sites. Binding of Ca2+ induced an increase in the alpha-helical content and a conformational change that lead to the exposure of hydrophobic regions responsible for target protein recognition. Cation binding, either Ca2+ or Mg2+, stabilized the secondary and tertiary structures of CML36, guiding a large structural transition from a molten globule apo-state to a compact holoconformation. Importantly, through in vitro binding and activity assays, we showed that CML36 interacts directly with the regulative N terminus of the Arabidopsis plasma membrane Ca2+-ATPase isoform 8 (ACA8) and that this interaction stimulates ACA8 activity. Gene expression analysis revealed that CML36 and ACA8 are co-expressed mainly in inflorescences. Collectively, our results support a role for CML36 as a Ca2+ sensor that binds to and modulates ACA8, uncovering a possible involvement of the CML protein family in the modulation of plant-autoinhibited Ca2+ pumps.
Arabidopsis Calmodulin-like Protein CML36 is a Calcium (Ca2+) Sensor that Interacts with the Plasma Membrane Ca2+-ATPase Isoform ACA8 and Stimulates its Activity / A. Astegno, M.C. Bonza, R. Vallone, V. La Verde, M. D’Onofrio, L. Luoni, B. Molesin, P. Dominici. - In: JOURNAL OF BIOLOGICAL CHEMISTRY. - ISSN 1083-351X. - 292:36(2017), pp. 15049-15061.
|Titolo:||Arabidopsis Calmodulin-like Protein CML36 is a Calcium (Ca2+) Sensor that Interacts with the Plasma Membrane Ca2+-ATPase Isoform ACA8 and Stimulates its Activity|
BONZA, MARIA CRISTINA (Secondo)
|Parole Chiave:||Plant glutamate-decarboxylase; ion-binding-properties; N-terminus; saccharomyces-cervisiae; reference genes; thaliana; expression; mechanism; NMR; magnesium|
|Settore Scientifico Disciplinare:||Settore BIO/04 - Fisiologia Vegetale|
Settore BIO/10 - Biochimica
|Data di pubblicazione:||2017|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1074/jbc.M117.787796|
|Appare nelle tipologie:||01 - Articolo su periodico|