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Under the control of lac or tac promoters, this gene, shc, was expressed in Escherichia coli K12 strains and its product had squalene-hopene cyclase activity. Sequence alignments with the A. acidocaldarius SHC, the lanosterol cyclase of the yeast Candida albicans, and the cycloartenol synthase of the plant Arabidopsis thaliana revealed six highly conserved regions (mainly in the C-terminal part) of the proteins. These regions contained the core motif Gln-X-X-X-G I y-X-Trp.

A set of vectors was constructed for the cloning and expression of heterologous genes in the Gram-negative bacterium Zymomonas mobilis under the control of the pdc promoter of Z. mobilis. The vectors pPTZ1, pPTZ3, and pPTZ4 are based on the cryptic Z. mobilis plasmid pZM02 and on parts of the Escherichia coli plasmids pKK223-3 and pBR322 together with the multiple cloning site of phage M13mp18. DNA fragments can be readily inserted immediately downstream from the pdc promoter at unique restriction sites for KpnI, XbaI and PstI in pPTZ1 and additionally for SmaI and BamHI in pPTZ3. In pPTZ4, the 5' terminal codons of pdc were deleted allowing the formation of gene fusions. Expression of a promoterless chloramphenicol acetyltransferase gene (cat) controlled by the pdc gene promoter resulted in enzyme activities of up to 5.5 U/mg total cell protein in Z. mobilis cells.