Regulation and Over-expression of the fnr Gene of Escherichia coli

Abstract

3279The fnr gene of Escherichia coli encodes a transcriptional activator (FNR) which is required for the expression of a number of genes involved in anaerobic respiratory pathways. From the study of a translational fusion of fnr to the gene for /3-galactosidase (ZacZ) it has been concluded that the fnr gene is expressed under both aerobic and anaerobic conditions and is subject to autoregulation and repression by glucose, particularly during anaerobic growth. These findings imply that during anaerobiosis the FNR protein adopts an active conformation, in which it functions both as a repressor of'the fnr gene and as an activator offitr-dependent genes. Sequences in the 5' non-coding region of fnr which could be involved in autoregulation are discussed. The fnr coding region was cloned into an expression vector which has allowed an amplification of FNR synthesis such that it accounts for about 2% of total cell protein. The ability to over-produce FNR in this way should be very useful for future biochemical studies.

Downregulation of Escherichia coli yfiD expression by FNR occupying a site at −93.5 involves the AR1‐containing face of FNR

“…␤-Galactosidase activity was determined according to Miller (1972). Western blotting of the soluble fractions of cell extracts obtained from stationary-phase cultures was as described by Spiro and Guest (1987) and indicated that expression of FNR, HlyX, FNR-HlyX hybrids and the FNR variants were similar, except S73→F and F92→S, which were present at Ϸ20% of the level observed with FNR. The EcoRI-BamHI yfiD promoter fragments of pGS1000 and pGS1052 were transferred to pUC118 to create pGS1036 and pGS1052a for sequencing and as source of promoter DNA for footprinting.…”

In vivo and in vitro mutants of FNR the anaerobic transcriptional regulator of E.coli

“…The template was an M13mp9 derivative containing an fnr gene with a unique Ncol site at the translation initiation site [4]. With S169, SSB (4 pg) was added to the template prior to oligonucleotide annealing.…”

“…The pUC and pBR322 derivatives expressing altered fnr genes were transformed into JRGl728( A luc afnr) (81 to test their ability to restore anaerobic growth on glycerol-fumarate medium [l 11, and for Western blotting to confirm that an FNR protein is produced [4].…”

“…FNR also regulates its own synthesis and represses the NADH dehydrogenase II gene, ndh, under anaerobic conditions [4,5]. It has been predicted that the FNR protein is structurally analogous to the CAMP receptor protein (CRP), which activates genes that are subject to catabolite repression (Fig.…”

Effect of the tor mutation in Escherichia coli on the trimethylamine N-oxide, nitrate and dimethylsulfoxide reductases, the formate dehydrogenases N and H and nitrate repression.

“…Fnr protein is involved in expression of narGHJI for nitrate reductase, frdABCD for fumarate reductase, nirB for nitrite reductase and so on (8,13,19,25,26)]. The ntrA gene product (NtrA) is required for the expression of the two enzymes of the formate hydrogenlyase system formate dehydrogenase H and hydrogenase 3 (3).…”