ISOLATION AND CHARACTERIZATION OF ZYMOMONAS MOBILIS DNA FRAGMENTS ACTING AS PROMOTER TRANSCRIPTIONAL ELEMENTS IN ESCHERICHIA COLI

Abstract

Promoter libraries of Zymomonas mobilis were generated in Escherichia coli using the CAT promoterless vector, pKK232-8. Among the 15 clones retained for further study, quantitative analysis of promoter strength revealed a 140-fold difference between the weakest and strongest promoter fragment. Nucleotide sequence determination and primer extension analysis were used to locate possible promoter-like sequences. Inspection of the DNA sequence surrounding the mRNA start-site, revealed regions similar to the E. coli sigma 70 consensus sequence (TTGACA-17bps- TATAAT), approximately 4-8bps upstream. Analogous to E. coli upstream activators, regions high in AT content (70-80%) and rich in static DNA bands, were found preceding the -35 hexamer. Only one promoter fragment clone (Z1) was found to carry an open reading frame preceded by a sequence resembling a ribosome-binding site with a free energy of SD-anti-SD binding (ΔG°) of -12.4kcal/mol.