Regulation of malate dehydrogenase (mdh) gene expression in Escherichia coli in response to oxygen, carbon, and heme availability

Abstract

Malate dehydrogenase catalyzes the interconversion of malate and oxaloacetate. It participates as a member of the tricarboxylic acid cycle and the branched noncyclic pathways under aerobic and anaerobic cell growth conditions, respectively. To investigate how the mdh gene is expressed under these different conditions, an mdh-lacZ operon fusion was constructed and analyzed in vivo. The mdh-lacZ fusion was expressed about twofold higher under aerobic conditions than under anaerobic cell growth conditions on most media tested. This anaerobic response is modulated by the ArcA protein, which functions as a repressor of mdh gene expression under both aerobic and anaerobic conditions. In contrast, mutations in the fnr gene did not affect mdh gene expression. Interestingly, cells grown anaerobically with glycerol and trimethylamine N-oxide or fumarate showed higher levels of mdh expression than did cells that were grown aerobically. Depending on the type of carbon compound used for cell growth, mdh expression varied by 11-fold and 5-fold under aerobic and anaerobic conditions, respectively. While mdh transcription was shown to be inversely proportional to the cell growth rate, cellular heme limitation stimulated a fivefold increase in mdh gene expression. The mdh gene appears to be highly regulated to adapt to changing conditions of aerobic and anaerobic cell growth with various types of carbon substrates.Malate dehydrogenase (EC 1.1.1.37) (MDH) is an essential enzyme in the tricarboxylic acid (TCA) cycle as well as the noncyclic anaplerotic pathway of Escherichia coli (15). It catalyzes the interconversion of malate and oxaloacetate with a concomitant reduction of NAD or oxidation of NADH. The reaction carried out by MDH under aerobic conditions in which the TCA cycle is operative is from malate to oxaloacetate (i.e., oxidation); the reaction proceeds in the opposite direction for participation in the branched noncyclic pathway. This pathway is considered to operate predominantly under anaerobic cell growth conditions (15). However, the effects of different environmental conditions on the regulation of mdh gene expression in E. coli or in other microorganisms have not been examined.The mdh gene in E. coli, which encodes MDH, is located at 70.6 min on the chromosome (8), and it has recently been cloned and sequenced (11,22). The E. coli enzyme is a dimeric enzyme with a molecular weight of 60,000 (13), like the MDHs isolated from most other organisms (14). It has a remarkable homology to the mitochondrial MDH (e.g., 59% amino acid identity to porcine mitochondrial MDH), especially in the nucleotide binding site located near the amino terminus of the protein. The E. coli enzyme shows a lower degree of sequence similarity to the alternative eucaryotic MDH isozyme that is cytoplasmically located (ca. 20% similarity to the porcine cytoplasmic MDH). The level of the E. coli MDH enzyme in the cell is reduced by anaerobiosis and glucose (6, 21) and induced by acetate and malate (21). In addition, MDH activity is elevated in ar...

Role of multiple ArcA recognition sites in anaerobic regulation of succinate dehydrogenase (sdhCDAB ) gene expression in Escherichia coli

“…Similar observations were made for several other TCA cycle genes, including gltA, mdh, fumA and icd Woods and Guest, 1994;Park and Gunsalus, 1995;Park et al, 1995b;Chao et al, 1997), as well as for some respiratory pathway genes, frdABCD, dmsABC and narGHJI (Jones and Gunsalus, 1987;Li and DeMoss, 1988;Cotter and Gunsalus, 1989;reviewed in Gunsalus and Park, 1994). The molecular basis for this ArcA-and Fnr-independent control is not well understood, but it may be related to minor effects of DNA supercoiling (Axley and Stadtman, 1988).…”

Aerobic regulation of the sucABCD genes of Escherichia coli, which encode alpha-ketoglutarate dehydrogenase and succinyl coenzyme A synthetase: roles of ArcA, Fnr, and the upstream sdhCDAB promoter

“…Since the ArcA and/or the Fnr proteins are known to regulate several TCA cycle genes, including the sdhCDAB, mdh, gltA, acnA, and fumAC genes, in E. coli in response to anaerobiosis (6,8,(16)(17)(18)(19)27), we examined the effects of arcA and fnr gene deletions on sucA-lacZ and sdhCDAB-sucA-lacZ expression (Table 4). In neither the arcA strain nor the fnr strain did sucA-lacZ expression vary significantly compared to that of the wild-type strain grown under aerobic or anaerobic conditions.…”

Function, kinetic properties, crystallization, and regulation of microbial malate dehydrogenase

“…In Thermus thermophilus, MDH had a higher expression level when it was grown on malate as the carbon source instead of glucose (Park and Kilbane II, 2004). In addition, mdh from E. coli is expressed at four-fold higher levels with pyruvate than with glucose under aerobic conditions (Park et al, 1995). When S. erythraea is grown in glucose, expression remains constant, whereas when grown in fructose, expression is induced (Mendoza et al, 2009).…”

“…The mdh expression can also be regulated by transcriptional factors. In E. coli, the expression is down-regulated by the aerobic respiration control protein (ArcA), particularly under anaerobic conditions (Park et al, 1995). When E. coli was grown on acid media, it raised not only the MDH activity but also the isocitrate dehydrogenase and succinate dehydrogenase activities (Jain et al, 2013).…”