Molecular cloning, overexpression, and characterization of autophosphorylation in calcium-dependent protein kinase 1 (CDPK1) from Cicer arietinum

Dixit, Ajay Kumar and Chelliah, Jayabaskaran (2013) Molecular cloning, overexpression, and characterization of autophosphorylation in calcium-dependent protein kinase 1 (CDPK1) from Cicer arietinum. In: Applied Microbiology and Biotechnology, 97 (8). pp. 3429-3439.

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Abstract

In plants, calcium-dependent protein kinases (CDPKs) are key intermediates in calcium-mediated signaling that couple changes in Ca2+ levels to a specific response. In the present study, we report the high-level soluble expression of calcium-dependent protein kinase1 from Cicer arietinum (CaCDPK1) in Escherichia coli. The expression of soluble CaCDPK1 was temperature dependent with a yield of 3-4 mg/l of bacterial culture. CaCDPK1 expressed as histidine-tag fusion protein was purified using Ni-NTA affinity chromatography till homogeneity. The recombinant CaCDPK1 protein exhibited both calcium-dependent autophosphorylation and substrate phosphorylation activities with a V (max) and K (m) value of 13.2 nmol/min/mg and 34.3 mu M, respectively, for histone III-S as substrate. Maximum autophosphorylation was seen only in the presence of calcium. Optimum temperature for autophosphorylation was found to be 37 A degrees C. The recombinant protein showed optimum pH range of 6-9. The role of autophosphorylation in substrate phosphorylation was investigated using histone III-S as exogenous substrate. Our results show that autophosphorylation happens before substrate phosphorylation and it happens via intra-molecular mechanism as the activity linearly depends on enzyme concentrations. Autophosphorylation enhances the kinase activity and reduces the lag phase of activation, and CaCDPK1 can utilize both ATP and GTP as phosphodonor but ATP is preferred than GTP.

Item Type:	Journal Article
Publication:	Applied Microbiology and Biotechnology
Publisher:	Springer
Additional Information:	Copyright of this article belongs to Springer.
Keywords:	Calcium; Calcium-Dependent Protein Kinases; Escherichia Coli; Expression; Purification; Ni-NTA Affinity; Autophosphorylation; Kinases
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	04 Jun 2013 09:43
Last Modified:	04 Jun 2013 09:43
URI:	http://eprints.iisc.ac.in/id/eprint/46518

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