An alkB gene homolog is differentially transcribed during the Caulobacter crescentus cell cycle

Colombi, Débora; Gomes, Suely L.

doi:10.1128/jb.179.10.3139-3145.1997

Cited by 29 publications

(23 citation statements)

References 36 publications

(45 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Sequences from the 3 kb 5Ј to the katG gene were not homologous to metL and metF, which are upstream of E. coli katG. It appears that the chromosomal organization around katG is different in the two species, as is the case for another C. crescentus stress response gene, alkB, in the response to alkylating agents (6).…”

Section: Resultsmentioning

confidence: 94%

“…However, with the C. crescentus katG:: lacZ fusion strain or wild-type strain CB15N, a 30-min induction with 60 M H 2 O 2 followed by 20 mM H 2 O 2 for 15 min gave the same survival (4 to 9%) as was obtained when induction was omitted. It is of interest that a similar situation holds for the response to alkylating agents, where C. crescentus, in contrast to E. coli, does not become resistant to lethal concentrations following exposure to low levels (6).…”

Section: Resultsmentioning

confidence: 95%

See 1 more Smart Citation

Catalase-peroxidase of Caulobacter crescentus: function and role in stationary-phase survival

1997

View full text Add to dashboard Cite

Caulobacter crescentus is an obligate aerobe which is exposed to high concentrations of photosynthetic oxygen and low levels of nutrients in its aquatic environment. Physiological studies of oxidative and starvation stresses in C. crescentus were undertaken through a study of lacZ fusion and null mutant strains constructed from the cloned 5 end of katG, encoding a catalase-peroxidase. The katG gene was shown to be solely responsible for catalase and peroxidase activity in C. crescentus. Like the katG of Escherichia coli, C. crescentus katG is induced by hydrogen peroxide and is important in sustaining the exponential growth rate. However, dramatic differences are seen in growth stage induction. E. coli KatE catalase and KatG catalase-peroxidase activities are induced 15-to 20-fold during exponential growth and then approximately halved in the stationary phase. In contrast, C. crescentus KatG activity is constant throughout exponential growth and is induced 50-fold in the stationary phase. Moreover, the survival of a C. crescentus katG null mutant is reduced by more than 3 orders of magnitude after 24 h in stationary phase and more than 6 orders of magnitude after 48 h, a phenotype not seen for E. coli katE and katG null mutants. These results indicate a major role for C. crescentus catalaseperoxidase in stationary-phase survival and raise questions about whether the peroxidatic activity as well as the protective catalatic activity of the dual-function enzyme is important in the response to starvation stress.Caulobacter crescentus is a gram-negative bacterium whose asymmetry of cell division and dimorphic life cycle are subjects of extensive investigation (27). By comparison, little is known about the physiology of Caulobacter. We have been interested in the response of C. crescentus to oxidative stress and starvation (26), salient features of its natural environment. As a freshwater pond bacterium, C. crescentus is frequently associated with cyanobacteria (2, 15), whose photosynthetic activity could expose the bacterium to high oxygen concentrations. As an organism adapted to nutrient-poor conditions (8,21,22), C. crescentus is likely to frequently enter and exit the stationary phase.Catalases and catalase-peroxidases have been studied in the context of oxidative and starvation (stationary phase) stress. Both enzymes catalyze H 2 O 2 decomposition. Stationary-phase induction, especially by catalases, is a hallmark of the multiple stress resistance acquired during starvation (13). Information about these activities in C. crescentus appears to be limited to the demonstration of catalase activity in a plate assay by Poindexter (21, 22) and our recent demonstration that a single catalase-peroxidase is present and is induced during stationary phase (26). The present work was undertaken to study the expression and function of this catalase-peroxidase in response to oxidative stress and during growth. We report here the cloning of the 5Ј end of the katG catalase-peroxidase gene and its constitutive expression during th...

show abstract

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 95%

Catalase-peroxidase of Caulobacter crescentus: function and role in stationary-phase survival

1997

View full text Add to dashboard Cite

show abstract

“…Sawant et al (2001) also found an adaptive response to low dose gamma irradiation of 10T1/2 cells that were subsequently exposed to microbeam alpha-particle irradiation. Other test systems under some experimental conditions may also not show an AR (Boreham and Mitchel, 1993;Colombi and Gomes, 1997;Zasukhina et al, 2000;Pelevina et al, 2003;Joksic and Petrovic, 2004).…”

Section: The Adaptive Responsementioning

confidence: 99%

Adaptive response: some underlying mechanisms and open questions

2008

View full text Add to dashboard Cite

Organisms are affected by different DNA damaging agents naturally present in the environment or released as a result of human activity. Many defense mechanisms have evolved in organisms to minimize genotoxic damage. One of them is induced radioresistance or adaptive response. The adaptive response could be considered as a nonspecific phenomenon in which exposure to minimal stress could result in increased resistance to higher levels of the same or to other types of stress some hours later. A better understanding of the molecular mechanism underlying the adaptive response may lead to an improvement of cancer treatment, risk assessment and risk management strategies, radiation protection, e.g. of astronauts during long-term space flights. In this mini-review we discuss some open questions and the probable underlying mechanisms involved in adaptive response: the transcription of many genes and the activation of numerous signaling pathways that trigger cell defenses -DNA repair systems, induction of proteins synthesis, enhanced detoxification of free radicals and antioxidant production.

show abstract

“…Homologs of AlkB have been discovered based on sequence and fold similarity, and it is now known that the alkB gene is conserved from bacteria to human [19,[33][34][35]. The homologs are not expressed equally in all human tissue types and may account for the discrepancies in function [36].…”

Section: Alkb Homologsmentioning

confidence: 99%

“…All homologs share the essential motifs and residues for enzymatic activity, consisting of a HXD motif, a single H, as well as a RXXXXXR motif where the X's within the two arginines are alternating hydrophobic and polar residues (Fig. 2) [19,[33][34][35]. The two histidines and the aspartic acid are proposed ligands to the active site Fe II , whereas the first arginine is predicted to be involved in binding to the αKG [19,37] and these residues are highly conserved in the αKG-dependent oxygenases.…”

Section: Alkb Homologsmentioning

confidence: 99%

Oxidative dealkylation DNA repair mediated by the mononuclear non-heme iron AlkB proteins

Mishina

2006

Journal of Inorganic Biochemistry

View full text Add to dashboard Cite

DNA can be damaged by various intracellular and environmental alkylating agents to produce alkylation base lesions. These base damages, if not repaired promptly, may cause genetic changes that lead to diseases such as cancer. Recently, it was discovered that some of the alkylation DNA base damage can be directly removed by a family of proteins called the AlkB proteins that utilize a mononuclear non-heme iron(II) and α-ketoglutarate as cofactor and cosubstrate. These proteins activate dioxygen and perform an unprecedented oxidative deal-kylation of the alkyl adducts on DNA heteroatoms. This review summarizes the discovery of this activity and the recent research advances in studying this unique DNA repair pathway. The focus is placed on the chemical mechanism and function of these proteins. KeywordsDNA repair; AlkB; ABH; Direct repair; Mononuclear non-heme iron; Dioxygenase; Oxidative dealkylation; Demethylation Direct repair of alkylation DNA damageCellular DNA is subject to nonenzymatic alkylation (methylation) by environmental or chemical mutagens, resulting in adducts that are toxic and mutagenic [1][2][3][4][5][6]. Organisms have evolved a variety of mechanisms to repair these mutagenic damages. Escherichia coli (E. coli) responds to this threat by activating an adaptive responsive pathway, mediated by the E. coli Ada protein [7]. Upon receiving a methyl group from the damaged DNA, Ada turns into a transcriptional activator and activates its own expression and that of the alkB gene and two other genes, alkA and aidB ( Fig. 1(a)) [4,7,8]. The upregulated Ada is a bifunctional protein, which uses a N-terminal Cys38 residue to remove a methyl group fromS p -methylphosphotriester and a C-terminal Cys321 residue to remove a methyl adduct from O 6 -methylguanaine ( Fig. 1(b)) [9][10][11]. Both repair functions are irreversible and represent rare examples of direct repair of DNA damage. AlkA is a glycosylase that cleaves methylated bases from DNA and performs the first step of the well-known base excision repair of base lesions [12][13][14]. The precise function of AidB is still unknown. The function of the last member of this adaptive response, AlkB, also remained unknown until recently despite extensive research efforts. E. coli AlkBSince the first genetic study in 1983 isolating the E. coli mutant with specific sensitivity to the alkylating agent methylmethane sulfonate, MMS [15], the activity of AlkB was undisclosed The Fe II /αKG-dependent dioxygenase superfamily is widespread from bacteria to humans [19] and is the largest known non-heme iron protein family [20][21][22][23]. It represents a wide diversity of enzymes that catalyze the hydroxylation of unactivated C-H groups of a variety of substrates by coupling reductive activation of dioxygen with a decarbox-ylation of αKG, the co-substrate, to succinate. In the event of oxidation one of the oxygen atoms from O 2 is incorporated into the succinate and the other as a hydroxyl in the product [24]. This group of enzymes is known for their importance in ...

show abstract

An alkB gene homolog is differentially transcribed during the Caulobacter crescentus cell cycle

Cited by 29 publications

References 36 publications

Catalase-peroxidase of Caulobacter crescentus: function and role in stationary-phase survival

Catalase-peroxidase of Caulobacter crescentus: function and role in stationary-phase survival

Adaptive response: some underlying mechanisms and open questions

Oxidative dealkylation DNA repair mediated by the mononuclear non-heme iron AlkB proteins

Contact Info

Product

Resources

About