U. Gerike et al., SEQUENCING AND EXPRESSION OF THE GENE ENCODING A COLD-ACTIVE CITRATE SYNTHASE FROM AN ANTARCTIC BACTERIUM, STRAIN DS2-3R, European journal of biochemistry, 248(1), 1997, pp. 49-57
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, p
urified from DS2-3R, are cold-active, with a temperature optimum of 31
degrees C. In addition the enzymes are rapidly inactivated at 45 degr
ees C, and show significant activity at 10 degrees C and below. Compar
ison of amino acid sequences indicates that DS2-3R citrate synthase is
most closely related to the enzyme from gram-positive bacteria. The a
mino acid sequence of the DS2-3R enzyme shows several features previou
sly recognised in other cold-active enzymes, including an extended sur
face loop, an increase in the occurrence of charged residues and a dec
rease in the number of proline residues in loops. Other changes observ
ed in some psychrophilic enzymes, such as a decrease in isoleucine con
tent and in arginine/(arginine + lysine) content, were not seen in thi
s case.