Characterization and enzymatic properties of protein kinase ACR4 from Arabidopsis thaliana

Serine/threonine-protein kinase-like protein ARABIDOPSIS CRINKLY4 (ACR4), a transmembrane protein of Arabidopsis thaliana, plays important roles in cell division and differentiation. Although accumulating studies shed light on the function of ACR4, the structure and catalytic mechanism of ACR4 remain to be elucidated. Here, we report the purification and enzymatic properties of the intracellular kinase domain (residues 464-799) of ACR4 (ACR4^IKD). Through Ni-affinity chromatography and gel filter chromatography methods, we successfully obtain high-purity ACR4^IKD protein from Escherichia coli. Dynamic light scattering and gel-filtration methods reveal that ACR4^IKD distributes with high homogeneity and exists as a monomer in solution. In addition, the ACR4^IKD protein has typical kinase activity with myelin basic protein (MBP) as the substrate. Our study may lay the foundation for structure determination of ACR4^IKD and further functional research, for example, screening significant substrates of ACR4 in Arabidopsis thaliana.