OXYGEN-DEPENDENT REGULATION OF VITREOSCILLA GLOBIN GENE - EVIDENCE FOR POSITIVE REGULATION BY FNR

Vitreoscilla globin (vgb) gene, encoding for Vitreoscilla haemoglobin (VtHb) has been cloned and functionally expressed in heterologous bact erial hosts. Analysis of vgb gene expression and the study on vgb-xylE transcriptional fusion revealed that vgb promoter is preferentially a ctivated in response to oxygen limitation in Vitreoscilla and other he terologous bacterial hosts. Microaerobic mode of induction in various hosts, provided evidence for a common regulatory factor involved in ac tivation of vgb promoter under hypoxic condition. Primary structure an alysis of vgb upstream regulatory region indicated the presence of a p ossible binding site for the transcriptional activator, FNR. Further, the E. coli mutant lacking fnr gene product was not able to activate v gb promoter under microaerobic condition, suggesting the involvement o f FNR or FNR-like proteins in modulating its activity. The possibility of a second level of control by CRP is also indicated. Oxygen respons ive nature and regulatory characteristics of vgb promoter offers a nov el system for the expression of gene in heterologous bacterial hosts i n an oxygen dependent manner. (C) 1994 Academic Press, Inc.