Sequencing and Expression of the Gene Encoding a Cold-Active Citrate Synthase from an Antarctic Bacterium, Strain DS2-3R

Authors


  • Note. The nucleotide sequence data published here have been deposited with the GenBank sequence data bank under the accession number U85944.

D. W. Hough, Department of Biology and Bio-chemistry, University of Bath, Bath, BA2 7AY, UK
Fax: +44 1225 826779.
E-mail: D.W.Hough@bath.ac.uk

Abstract

The gene encoding citrate synthase from a novel bacterial isolate (DS2-3R) from Antarctica has been cloned, sequenced and over expressed in Escherichia coli. Both the recombinant enzyme and the native enzyme, purified from DS2-3R, are cold-active, with a temperature optimum of 31°C. In addition the enzymes are rapidly inactivated at 45°C, and show significant activity at 10°C and below. Comparison of amino acid sequences indicates that DS2-3R citrate synthase is most closely related to the enzyme from gram-positive bacteria. The amino acid sequence of the DS2-3R enzyme shows several features previously recognised in other cold-active enzymes, including an extended surface loop, an increase in the occurrence of charged residues and a decrease in the number of proline residues in loops. Other changes observed in some psychrophilic enzymes, such as a decrease in isoleucine content and in arginine/(arginine+lysine) content, were not seen in this case.

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