Characterization of CaMKIIα holoenzyme stability. (2nd May 2020)

• Record Type: Journal Article
• Authors: Torres‐Ocampo, Ana P.; Özden, Can; Hommer, Alexandra; Gardella, Anne; Lapinskas, Emily; Samkutty, Alfred; Esposito, Edward; Garman, Scott C; Stratton, Margaret M
• Is Part Of: Protein science. Volume 29:Number 6(2020)
• Page Start: 1524
• Page End: 1534
• Publication Date: 2020-05-02
• Subjects: CaMKII -- differential scanning calorimetry -- mass photometry -- oligomer dissociation -- thermal stability; Proteins -- Periodicals; 572.6
• DOI: 10.1002/pro.3869
• Languages: English
• ISSNs: 0961-8368

Abstract

Abstract: Ca 2+ /calmodulin‐dependent protein kinase II (CaMKII) is a Ser/Thr kinase necessary for long‐term memory formation and other Ca 2+ ‐dependent signaling cascades such as fertilization. Here, we investigated the stability of CaMKIIα using a combination of differential scanning calorimetry (DSC), X‐ray crystallography, and mass photometry (MP). The kinase domain has a low thermal stability (apparent T m = 36°C), which is slightly stabilized by ATP/MgCl2 binding (apparent T m = 40°C) and significantly stabilized by regulatory segment binding (apparent T m = 60°C). We crystallized the kinase domain of CaMKII bound to p ‐coumaric acid in the active site. This structure reveals solvent‐exposed hydrophobic residues in the substrate‐binding pocket, which are normally buried in the autoinhibited structure when the regulatory segment is present. This likely accounts for the large stabilization that we observe in DSC measurements comparing the kinase alone with the kinase plus regulatory segment. The hub domain alone is extremely stable (apparent T m ~ 90°C), and the holoenzyme structure has multiple unfolding transitions ranging from ~60°C to 100°C. Using MP, we compared a CaMKIIα holoenzyme with different variable linker regions and determined that the dissociation of both these holoenzymes occurs at a higher concentration (is less stable) compared with the hub domain alone. We conclude that within the context of the holoenzyme structure, the kinase domain is stabilized, whereas the hub domain is destabilized. These data support a model where domains within the holoenzyme interact.