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PubMed2006

Complete genome sequence of the dehalorespiring bacterium Desulfitobacterium hafniense Y51 and comparison with Dehalococcoides ethenogenes 195.

Desulfitobacterium strains have the ability to dechlorinate halogenated compounds under anaerobic conditions by dehalorespiration. The complete genome of the tetrachloroethene (PCE)-dechlorinating strain Desulfitobacterium hafniense Y51 is a 5,727,534-bp circular chromosome harboring 5,060 predicted protein coding sequences. This genome contains only two reductive dehalogenase genes, a lower number than reported in most other dehalorespiring strains. More than 50 members of the dimethyl sulfoxide reductase superfamily and 30 paralogs of the flavoprotein subunit of the fumarate reductase are encoded as well. A remarkable feature of the genome is the large number of O-demethylase paralogs, which allow utilization of lignin-derived phenyl methyl ethers as electron donors. The large genome reveals a more versatile microorganism that can utilize a larger set of specialized electron donors and acceptors than previously thought. This is in sharp contrast to the PCE-dechlorinating strain Dehalococcoides ethenogenes 195, which has a relatively small genome with a narrow metabolic repertoire. A genomic comparison of these two very different strains allowed us to narrow down the potential candidates implicated in the dechlorination process. Our results provide further impetus to the use of desulfitobacteria as tools for bioremediation.

Chloroflexi↗
PubMed2005

Molecular analysis of Desulfitobacterium frappieri pcp-1 involved in reductive dehalogenation of pentachlorophenol.

Desulfitobacterium are Gram positive, spore-forming, strictly anaerobic bacteria, that belong to the Firmicutes, Clostridia, Clostridiales, and Peptococcaceae. Most known members of the genus Desulfitobacterium have the ability to dechlorinate several halogenated compounds by a mechanism of reductive dehalogenation and use them as electron acceptors to generate energy (halorespiration). Desulfitobacteria are therefore perfect candidates to be used in bioremediation treatments of environment polluted with halogenated compounds. Understanding the physiology and the molecular mechanisms of these bacteria will help to develop better bioremediation systems. This report summarizes works that have been done in our laboratories with D. frappieri PCP-1 on reductive dehalogenases, genes encoding these dehalogenases and their expression, and the development of lab-scale PCP-degrading reactors using this bacterium.

Biodegradation, Environmental↗
PubMed2001

Analysis of a 2,4,6-trichlorophenol-dehalogenating enrichment culture and isolation of the dehalogenating member Desulfitobacterium frappieri strain TCP-A.

An anaerobic, 2,4,6-trichlorophenol ortho-dehalogenating mixed culture was enriched from sediment of the river Saale (Germany). Two isolated dechlorinating colonies (MK1 and MK2) consisted of rods of different lengths and thicknesses, indicating heterogeneity. Following subcultivation with thiosulfate as alternative electron acceptor and cocultivation with Clostridium celerecrescensT, the 2,4,6-trichlorophenol-dehalogenating bacterium Desulfitobacterium frappieri strain TCP-A was isolated and characterized regarding its taxonomic properties and the spectrum of chlorophenols that it dehalogenated. Four other bacterial strains were coenriched and identified as organisms with closest phylogenetic relatedness to the Clostridium type strains C. indolis, C. glycolicum, C. hydroxybenzoicum and C. sporosphaeroides (16S rDNA sequence identities of 99.5, 99.2, 94.4, and 93.5%, respectively). Amplified ribosomal DNA restriction analysis of the original dehalogenating cultures MK1 and MK2 (when not exposed to thiosulfate) confirmed the microbial heterogeneity and revealed the presence of two additional species related to the type strains of C. celerecrescens and Clostridium propionicum. Only one copy of the 16S rRNA genes of Desulfitobacterium frappieri in each of the clone libraries of MK1 and MK2 (containing 136 and 56 clones, respectively) was found by dot-blot hybridization, suggesting a relatively low number of the dehalogenating bacterium within the enrichment culture.

Anaerobiosis↗
PubMed1996

Desulfitobacterium sp. strain PCE1, an anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene or ortho-chlorinated phenols.

A strictly anaerobic bacterium, strain PCE1, was isolated from a tetrachloroethene-dechlorinating enrichment culture. Cells of the bacterium were motile curved rods, with approximately four lateral flagella. They possessed a gram-positive type of cell wall and contained cytochrome c. Optimum growth occurred at pH 7.2-7.8 and 34-38 degrees C. The organism grew with L-lactate, pyruvate, butyrate, formate, succinate, or ethanol as electron donors, using either tetrachloroethene, 2-chlorophenol, 2,4,6-trichlorophenol, 3-chloro-4-hydroxy-phenylacetate, sulfite, thiosulfate, or fumarate as electron acceptors. Strain PCE1 also grew fermentatively with pyruvate as the sole substrate. L-Lactate and pyruvate were oxidized to acetate. Tetrachloroethene was reductively dechlorinated to trichloroethene and small amounts ( 5%) of cis-1,2-dichloroethene and trans-1,2-dichloroethene. Chlorinated phenolic compounds were dechlorinated specifically at the ortho-position. On the basis of 16S rRNA sequence analysis, the organism was identified as a species within the genus Desulfitobacterium, which until now only contained the chlorophenol-dechlorinating bacterium, Desulfitobacterium dehalogenans.

Bacteria, Anaerobic↗
PubMed2003

Purification, cloning and sequencing of an enzyme mediating the reductive dechlorination of 2,4,6-trichlorophenol from Desulfitobacterium frappieri PCP-1.

A new membrane-associated 2,4,6-trichlorophenol reductive dehalogenase from Desulfitobacterium frappieri PCP-1 was isolated. Initial characterization of the crude preparation showed that the dechlorinating activity was sensitive to oxygen, and its optimum pH was 7.0. Its dechlorinating activity was not inhibited by sulphate, was completely inhibited by 1 mM sulphite, and partially inhibited by 5 mM sodium azide and by more than 5 mM nitrate. Several polychlorophenols were dechlorinated in the ortho position with respect to the hydroxy group. A dehalogenase was purified to apparent homogeneity. SDS gel electrophoresis revealed a single protein band with a molecular mass of 37 kDa. However, after two-dimensional gel electrophoresis, this band was composed of three isoforms. MS analyses showed that the three isoforms were from the same protein and the molecular mass of the most abundant isoform is 33800 Da. A mixture of iodopropane and titanium citrate caused a light-reversible inhibition of the dechlorinating activity, suggesting the involvement of a corrinoid cofactor. The apparent K(m) value for 2,4,6-trichlorophenol and pentachlorophenol were 18.3+/-2.8 microM and 26.8+/-2.9 microM respectively, at a methyl viologen concentration of 2 mM. The N-terminal amino acid sequence and an internal tryptic peptide sequence were determined. One open reading frame (ORF) was found in the Desulfitobacterium hafniense genome containing these peptides sequences. The corresponding ORF in D. frappieri PCP-1 was cloned and sequenced. This ORF, that we designated crdA, showed no homology with any known dehalogenase, suggesting a distinct reductive dehalogenase.

Amino Acid Sequence↗
PubMed2001

Coexistence of a sulphate-reducing Desulfovibrio species and the dehalorespiring Desulfitobacterium frappieri TCE1 in defined chemostat cultures grown with various combinations of sulfate and tetrachloroethene.

A two-member co-culture consisting of the dehalorespiring Desulfitobacterium frappieri TCE1 and the sulphate-reducing Desulfovibrio sp. strain SULF1 was obtained via anaerobic enrichment from soil contaminated with tetrachloroethene (PCE). In this co-culture, PCE dechlorination to cis-dichloroethene was due to the activity of the dehalorespiring bacterium only. Chemostat experiments with lactate as the primary electron donor for both strains along with varying sulphate and PCE concentrations showed that the sulphate-reducing strain outnumbered the dehalogenating strain at relatively high ratios of sulphate/PCE. Stable co-cultures with both organisms present at similar cell densities were observed when both electron acceptors were supplied in the reservoir medium in nearly equimolar amounts. In the presence of low sulphate/PCE ratios, the Desulfitobacterium sp. became the numerically dominant strain within the chemostat co-culture. Surprisingly, in the absence of sulphate, strain SULF1 did not disappear completely from the co-culture despite the fact that there was no electron acceptor provided with the medium to be used by this sulphate reducer. Therefore, we propose a syntrophic association between the sulphate-reducing and the dehalorespiring bacteria via interspecies hydrogen transfer. The sulphate reducer was able to sustain growth in the chemostat co-culture by fermenting lactate and using the dehalogenating bacterium as a 'biological electron acceptor'. This is the first report describing growth of a sulphate-reducing bacterium in a defined two-member continuous culture by syntrophically coupling the electron and hydrogen transfer to a dehalorespiring bacterium.

Anaerobiosis↗
PubMed2002

Molecular characterization of the PceA reductive dehalogenase of desulfitobacterium sp. strain Y51.

The tetrachloroethene (PCE) reductive dehalogenase (encoded by the pceA gene and designated PceA dehalogenase) of Desulfitobacterium sp. strain Y51 was purified and characterized. The expression of the enzyme was highly induced in the presence of PCE and trichloroethene (TCE). The purified enzyme catalyzed the reductive dehalogenation of PCE via TCE to cis-1,2-dichloroethene at a specific activity of 113.6 nmol x min(-1) x mg of protein(-1). The apparent K(m) values for PCE and TCE were 105.7 and 535.3 microM, respectively. Chlorinated ethenes other than PCE and TCE were not dehalogenated. However, the enzyme exhibited dehalogenation activity for various chlorinated ethanes such as hexachloroethane, pentachloroethane, 1,1,1,2-tetrachloroethane, and 1,1,2,2-tetrachloroethane. The pceA gene of Desulfitobacterium sp. strain Y51 was identified in a 2.8-kb DNA fragment and used to express the protein in Escherichia coli for the preparation of antibodies. Immunoblot analyses located PceA in the periplasm of the cell.

Amino Acid Sequence↗
PubMedDate not supplied

Cyanophycin synthetase-like enzymes of non-cyanobacterial eubacteria: characterization of the polymer produced by a recombinant synthetase of Desulfitobacterium hafniense.

Some bacterial genomes were found to contain genes encoding putative proteins with considerable sequence homology to cyanophycin synthetase CphA of cyanobacteria. Such a gene from the Gram-positive, spore-forming anaerobe Desulfitobacterium hafniense was cloned. Expression in Escherichia coli resulted in the formation of a polydispers copolymer of aspartic acid and arginine, with a minor amount of lysine, of about 30 kDa molecular mass. In contrast to cyanophycin, this polymer was water-soluble. The structure of the polymer formed by the synthetase from Desulfitobacterium hafniense was studied by enzymatic degradation with the cyanophycin-specific hydrolase cyanophycinase, and by chemical and mass-spectroscopic analyses. Despite of the differences in solubility, indicating that both polymers cannot be completely identical, the chemical structure was found to be very similar to that of cyanophycin. The results suggest that the use of cyanophycin-like polymers as a nitrogen-rich reserve material is not restricted to cyanobacteria, and that such polymers may not necessarily be stored in granules.

Amino Acid Sequence↗
PubMed2005

Emergence of two types of nondechlorinating variants in the tetrachloroethene-halorespiring Desulfitobacterium sp. strain Y51.

Desulfitobacterium sp. strain Y51 exhibits a strong dechlorinating activity for tetrachloroethene (PCE), converting it to cis-1,2-dichloroethene via trichloroethene by the action of the PceA reductive dehalogenase (encoded by pceA). The gene organization around the pceA gene cluster was determined to be in the following order: orf4, orf3, ISDesp1, pceA-B-C-T-mcpA, and ISDesp2, where the pceA gene cluster is surrounded by two nearly identical copies of the ISDesp insertion sequence. Serial subculture of strain Y51 gave rise to variants that abolished the PCE-dechlorination activity. Southern hybridization analysis revealed two types of variants termed small deletion (SD) and large deletion (LD). The characterization of both variants revealed a genetic rearrangement around the pceAB gene cluster. In variant SD, ISDesp1 comprised of 1,572 bp was deleted, which includes the tnpAa encoding IS256 family transposase and unknown orf1. The ISDesp1 contained the inverted terminal repeat sequence and a -35 promoter stretch just upstream of the pceA gene, indicating that this IS element is involved in the formation of the variant SD. Loss of the pceA transcription changed the variant SD to the PCE-nondechlorinating phenotype. The variant LD lost the 6.5-kb region, including one copy of ISDesp and the pceABCT-mcpA gene cluster, confirming that the homologous recombination is associated with the emergence of this variant.

Base Sequence↗
PubMed2006

Sustained generation of electricity by the spore-forming, Gram-positive, Desulfitobacterium hafniense strain DCB2.

Desulfitobacterium hafniense strain DCB2 generates electricity in microbial fuel cells (MFCs) when humic acids or the humate analog anthraquinone-2,6-disulfonate (AQDS) is added as an electron-carrying mediator. When utilizing formate as fuel, the Gram-positive, spore-forming bacterium generated up to 400 mW/m2 of cathode surface area in a single-chamber MFC with a platinum-containing air-fed cathode. Hydrogen, lactate, pyruvate, and ethanol supported electricity generation, but acetate, propionate, and butyrate did not. Scanning electron microscopy indicated that strain DCB2 colonized the surface of a current-generating anode but not of an unconnected electrode. The electricity was recovered fully within minutes after the exchange of the medium in the anode chamber and within a week after an exposure of a colonized anode to 90 degrees C for 20 min. Of the six strains of Desulfitobacteria tested, all of which would reduce AQDS, only D. hafniense strain DCB2 continued to reduce AQDS and generate electricity for more than 24 h, indicating that reduction of the humate analog alone is insufficient to sustain electrode reduction.

Anthraquinones↗
PubMed2005

Biochemical and molecular characterization of a tetrachloroethene dechlorinating Desulfitobacterium sp. strain Y51: a review.

A strict anaerobic bacterium, Desulfitobacterium sp. strain Y51, is capable of very efficiently dechlorinating tetrachloroethene (PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (cis-DCE) at concentrations as high as 960 microM and as low as 0.06 microM. Dechlorination was highly susceptible to air oxidation and to potential alternative electron acceptors, such as nitrite, nitrate or sulfite. The PCE reductive dehalogenase (encoded by the pceA gene and abbreviated as PceA dehalogenase) of strain Y51 was purified and characterized. The purified enzyme catalyzed the reductive dechlorination of PCE to cis-DCE at a specific activity of 113.6 nmol min(-1) mg protein(-1). The apparent K(m) values for PCE and TCE were 105.7 and 535.3 microM, respectively. In addition to PCE and TCE, the enzyme exhibited dechlorination activity for various chlorinated ethanes such as hexachloroethane, pentachloroethane, 1,1,1,2-tetrachloroethane and 1,1,2,2-tetrachloroethane. An 8.4-kb DNA fragment cloned from the Y51 genome revealed eight open reading frames, including the pceAB genes. Immunoblot analysis revealed that PceA dehalogenase is localized in the periplasm of Y51 cells. Production of PceA dehalogenase was induced upon addition of TCE. Significant growth inhibition of strain Y51 was observed in the presence of cis-DCE, More interestingly, the pce gene cluster was deleted with high frequency when the cells were grown with cis-DCE.

Amino Acid Sequence↗
PubMed2004

Development of a real-time PCR method for quantification of the three genera Dehalobacter, Dehalococcoides, and Desulfitobacterium in microbial communities.

We developed standard curves based on plasmids containing a 16S rRNA gene of a member of one of the three genera Dehalobacter, Desulfitobacterium, and Dehalococcoides. A large difference in amplification efficiency between the standard curves was observed ranging from 1.5 to 2.0. The total eubacterial 16S rRNA gene copy number determined in a sample DNA by using eubacterial primers and the three standard curves led to differences in the estimated copy numbers of a factor up to 73. However, the amplification efficiencies for one specific standard curve were the same independent of the PCR primer pair used. This allowed the determination of the abundance of a population expressed as fractional number, hence, the percentage of genus-specific copy numbers within the total eubacterial 16S rRNA gene copy numbers. Determination of the fractional numbers in DNA mixtures of known composition showed the accuracy of this approach. The average difference in threshold value between two 10-fold dilutions of DNA of pure cultures, mixtures thereof and of environmental samples was -3.45+/-0.34, corresponding to an average almost optimal amplification efficiency of 1.95. This indicated that the low amplification efficiency of certain standard curves seemed to be mainly a problem of the plasmid DNA used and not of the 16S rRNA gene of the target genera.

Bacteria, Anaerobic↗
PubMed2006

Real time PCR quantification in groundwater of the dehalorespiring Desulfitobacterium dichloroeliminans strain DCA1.

Quantifying microorganisms responsible for bioremediation can provide insight in their behavior and can help to obtain a better understanding of the physicochemical parameters monitored during bioremediation. A real time PCR (RTm PCR) assay based on the detection with SYBR Green I was optimized in order to quantify the 1,2-dichloroethane dehalorespiring Desulfitobacterium dichloroeliminans strain DCA1. A primer pair targeting unique regions of the 16 S rRNA gene was designed and tested in silico for its specificity. Selectivity was furthermore evaluated and a Limit of Quantification of 1.5 x 10(4) cells/microL DNA extract was obtained for spiked groundwater. Real time measurements of groundwater samples retrieved from a bioaugmented monitoring well and which had an average concentration lying in the range of the Limit of Quantification were evaluated positively with regards to reproducibility. Validation of the RTm PCR assay on groundwater samples originating from different sites confirmed the specificity of the designed primer pair. This RTm PCR assay can be used to survey the abundance and kinetics of strain DCA1 in in situ bioaugmentation field studies.

Benzothiazoles↗
PubMed2006

Activity of Desulfitobacterium sp. strain Viet1 demonstrates bioavailability of 2,4-dichlorophenol previously sequestered by the aquatic plant Lemna minor.

Aquatic plants take up and sequester organic contaminants such as chlorophenols through incorporation in cell wall materials and storage in vacuoles. The ultimate fate of plant-sequestered chlorophenols, however, remains unclear. This research investigated 2,4-dichlorophenol (2,4-DCP) sequestration by the aquatic plant Lemna minor and evaluated contaminant release and bioavailability after plant death and cellular disruption. 14C-labeled 2,4-DCP was used to establish that contaminant removed from the aqueous phase was retained internal to L. minor. An assay with Desulfitobacterium sp. strain Viet1 was used to assess the readily bioavailable fraction of plant-sequestered 2,4-DCP and plant metabolites of 2,4-DCP. In plant-free systems, strain Viet1 dechlorinated 2,4-DCP to stoichiometric amounts of 4-chlorophenol (4-CP) as a stable and quantifiable end product. Anaerobic microcosms containing inactivated L. minor, which had accumulated 3.8 micromol of 2,4-DCP equivalents/g of plant material (fresh weight) during a preceding aerobic exposure, were inoculated with strain Viet1. After 118 d of incubation with strain Viet1, 43.5% (+/-1.4%) of the contaminant was recovered as 4-CP, indicating a large portion of plant-sequestered 2,4-DCP was bioavailable for dechlorination by strain Viet1. In contrast, 4-CP formation was not observed in autoclaved microcosms, and only 26.1% (+/-1.0%) of plant-sequestered 2,4-DCP was recovered in the aqueous phase. These findings demonstrate contaminant cycling between plants and microorganisms, and emphasize that understanding the mechanisms and pathways of contaminant sequestration by plants is critical for predicting long-term contaminant fate.

Biological Availability↗
PubMed2006

Transport and activity of Desulfitobacterium dichloroeliminans strain DCA1 during bioaugmentation of 1,2-DCA-contaminated groundwater.

The transport and activity of Desulfitobacterium dichloroeliminans strain DCA1 in 1,2-dichloroethane (1,2-DCA)-contaminated groundwater have been evaluated through an in situ bioaugmentation test at an industrial site (Belgium). The migration of strain DCA1 was monitored from an injection well toward a monitoring well, and the effect of the imposed groundwater flow on its distribution was assessed by means of transport model MOCDENS3D. The results of the real-time PCR (16S rRNA gene) quantification downstream from the injection point were used to evaluate the bacterial distribution pattern simulated by MOCDENS3D. In the injection well, the 1,2-DCA concentration in the groundwater decreased from 939.8 to 0.9 microM in a 35 day time interval and in the presence of a sodium lactate solution. Moreover, analyses from the monitoring well showed that the cells were still active after transport through the aquifer, although biodegradation occurred to a lesser extent. This study showed that strain DCA1 can be successfully applied for the removal of 1,2-DCA under field conditions and that its limited retardation offers perspectives for large-scale cleanup processes of industrial sites.

Chromatography, Gas↗
PubMed2006

Effects of chloromethanes on growth of and deletion of the pce gene cluster in dehalorespiring Desulfitobacterium hafniense strain Y51.

The dehalorespiring Desulfitobacterium hafniense strain Y51 efficiently dechlorinates tetrachloroethene (PCE) to cis-1,2-dichloroethene (cis-DCE) via trichloroethene by PceA reductive dehalogenase encoded by the pceA gene. In a previous study, we found that the significant growth inhibition of strain Y51 occurred in the presence of commercial cis-DCE. In this study, it turned out that the growth inhibition was caused by chloroform (CF) contamination of cis-DCE. Interestingly, CF did not affect the growth of PCE-nondechlorinating SD (small deletion) and LD (large deletion) variants, where the former fails to transcribe the pceABC genes caused by a deletion of the promoter and the latter lost the entire pceABCT gene cluster. Therefore, PCE-nondechlorinating variants, mostly LD variant, became predominant, and dechlorination activity was significantly reduced in the presence of CF. Moreover, such a growth inhibitory effect was also observed in the presence of carbon tetrachloride at 1 microM, but not carbon dichloride even at 1 mM.

Base Sequence↗
PubMed2005

Desulfitobacterium hafniense is present in a high proportion within the biofilms of a high-performance pentachlorophenol-degrading, methanogenic fixed-film reactor.

We developed a pentachlorophenol (PCP)-degrading, methanogenic fixed-film reactor by using broken granular sludge from an upflow anaerobic sludge blanket reactor. This methanogenic consortium was acclimated with increasing concentrations of PCP. After 225 days of acclimation, the reactor was performing at a high level, with a PCP removal rate of 1,173 muM day(-1), a PCP removal efficiency of up to 99%, a degradation efficiency of approximately 60%, and 3-chlorophenol as the main chlorophenol residual intermediate. Analyses by PCR-denaturing gradient gel electrophoresis (DGGE) showed that Bacteria and Archaea in the reactor stabilized in the biofilms after 56 days of operation. Important modifications in the profiles of Bacteria between the original granular sludge and the reactor occurred, as less than one-third of the sludge DGGE bands were still present in the reactor. Fluorescence in situ hybridization experiments with probes for Archaea or Bacteria revealed that the biofilms were composed mostly of Bacteria, which accounted for 70% of the cells. With PCR species-specific primers, the presence of the halorespiring bacterium Desulfitobacterium hafniense in the biofilm was detected very early during the reactor acclimation period. D. hafniense cells were scattered in the biofilm and accounted for 19% of the community. These results suggest that the presence of PCP-dehalogenating D. hafniense in the biofilm was crucial for the performance of the reactor.

Anaerobiosis↗
PubMed2006

Characterization of CprK1, a CRP/FNR-type transcriptional regulator of halorespiration from Desulfitobacterium hafniense.

The recently identified CprK branch of the CRP (cyclic AMP receptor protein)-FNR (fumarate and nitrate reduction regulator) family of transcriptional regulators includes proteins that activate the transcription of genes encoding proteins involved in reductive dehalogenation of chlorinated aromatic compounds. Here we report the characterization of the CprK1 protein from Desulfitobacterium hafniense, an anaerobic low-G+C gram-positive bacterium that is capable of reductive dechlorination of 3-chloro-4-hydroxyphenylacetic acid (Cl-OHPA). The gene encoding CprK1 was cloned and functionally overexpressed in Escherichia coli, and the protein was subsequently purified to homogeneity. To investigate the interaction of CprK1 with three of its predicted binding sequences (dehaloboxes), we performed in vitro DNA-binding assays (electrophoretic mobility shift assays) as well as in vivo promoter probe assays. Our results show that CprK1 binds its target dehaloboxes with high affinity (dissociation constant, 90 nM) in the presence of Cl-OHPA and that transcriptional initiation by CprK1 is influenced by deviations in the dehaloboxes from the consensus TTAAT----ATTAA sequence. A mutant CprK1 protein was created by a Val-->Glu substitution at a conserved position in the recognition alpha-helix that gained FNR-type DNA-binding specificity, recognizing the TTGAT----ATCAA sequence (FNR box) instead of the dehaloboxes. CprK1 was subject to oxidative inactivation in vitro, most likely caused by the formation of an intermolecular disulfide bridge between Cys11 and Cys200. The possibility of redox regulation of CprK1 by a thiol-disulfide exchange reaction was investigated by using two Cys-->Ser mutants. Our results indicate that a Cys11-Cys200 disulfide bridge does not appear to play a physiological role in the regulation of CprK1.

Amino Acid Sequence↗