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J. Bacteriol., Jun 1997, 3632-3638, Vol 179, No. 11
DA Bochar, JR Brown, WF Doolittle, HP Klenk, W Lam, ME Schenk, CV Stauffacher and VW Rodwell
The gene (hmgA) for 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA)
reductase (EC 1.1.1.34) from the thermophilic archaeon Sulfolobus
solfataricus P2 was cloned and sequenced. S. solfataricus HMG-CoA reductase
exhibited a high degree of sequence identity (47%) to the HMG- CoA
reductase of the halophilic archaeon Haloferax volcanii. Phylogenetic
analyses of HMG-CoA reductase protein sequences suggested that the two
archaeal genes are distant homologs of eukaryotic genes. The only known
bacterial HMG-CoA reductase, a strictly biodegradative enzyme from
Pseudomonas mevalonii, is highly diverged from archaeal and eukaryotic
HMG-CoA reductases. The S. solfataricus hmgA gene encodes a true
biosynthetic HMG-CoA reductase. Expression of hmgA in Escherichia coli
generated a protein that both converted HMG-CoA to mevalonate and
cross-reacted with antibodies raised against rat liver HMG-CoA reductase.
S. solfataricus HMG-CoA reductase was purified in 40% yield to a specific
activity of 17.5 microU per mg at 50 degrees C by a sequence of steps that
included heat treatment, ion-exchange chromatography, hydrophobic
interaction chromatography, and affinity chromatography. The final product
was homogeneous, as judged by sodium dodecyl sulfate-polyacrylamide gel
electrophoresis. The substrate was (S)- not (R)-HMG-CoA; the reductant was
NADPH not NADH. The Km values for HMG-CoA (17 microM) and NADPH (23 microM)
were similar in magnitude to those of other biosynthetic HMG-CoA
reductases. Unlike other HMG-CoA reductases, the enzyme was stable at 90
degrees C and was optimally active at pH 5.5 and 85 degrees C.
Copyright © 1997, American Society for Microbiology
3-hydroxy-3-methylglutaryl coenzyme A reductase of Sulfolobus solfataricus: DNA sequence, phylogeny, expression in Escherichia coli of the hmgA gene, and purification and kinetic characterization of the gene product
Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA.
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