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Preliminary X-ray crystallographic studies on acetate kinase (AckA) from Salmonella typhimurium in two crystal forms

Chittori, Sagar and Savithri, HS and Murthy, MRN (2011) Preliminary X-ray crystallographic studies on acetate kinase (AckA) from Salmonella typhimurium in two crystal forms. In: Acta Crystallographica Section F, 67 (Part 1). pp. 1658-1661.

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Abstract

Acetate kinase (AckA) catalyzes the reversible transfer of a phosphate group from acetyl phosphate to ADP, generating acetate and ATP, and plays a central role in carbon metabolism. In the present work, the gene corresponding to AckA from Salmonella typhimurium (StAckA) was cloned in the IPTG-inducible pRSET C vector, resulting in the attachment of a hexahistidine tag to the N-terminus of the expressed enzyme. The recombinant protein was overexpressed, purified and crystallized in two different crystal forms using the microbatch-under-oil method. Form I crystals diffracted to 2.70 angstrom resolution when examined using X-rays from a rotating-anode X-ray generator and belonged to the monoclinic space group C2, with unit-cell parameters a = 283.16, b = 62.17, c = 91.69 angstrom, beta = 93.57 degrees. Form II crystals, which diffracted to a higher resolution of 2.35 angstrom on the rotating-anode X-ray generator and to 1.90 angstrom on beamline BM14 of the ESRF, Grenoble, also belonged to space group C2 but with smaller unit-cell parameters (a = 151.01, b = 78.50, c = 97.48 angstrom, beta = 116.37 degrees). Calculation of Matthews coefficients for the two crystal forms suggested the presence of four and two protomers of StAckA in the asymmetric units of forms I and II, respectively. Initial phases for the form I diffraction data were obtained by molecular replacement using the coordinates of Thermotoga maritima AckA (TmAckA) as the search model. The form II structure was phased using a monomer of form I as the phasing model. Inspection of the initial electron-density maps suggests dramatic conformational differences between residues 230 and 300 of the two crystal forms and warrants further investigation.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to John Wiley & Sons.
Keywords: Salmonella typhimurium;short-chain fatty acids;tricarboxylic; citric acid cycle;acetate metabolism;acetate kinase;conformational changes
Department/Centre: Division of Biological Sciences > Biochemistry
Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 03 Jan 2012 12:24
Last Modified: 03 Jan 2012 12:28
URI: http://eprints.iisc.ernet.in/id/eprint/42964

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