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PubMed2002

Nitric oxide signaling and NO dependent transcriptional control in bacterial denitrification by members of the FNR-CRP regulator family.

Bacterial denitrification transforms nitrate to dinitrogen. The process is expressed facultatively in response to environmental conditions. Around 50 components make up the denitrification apparatus and its assembly pathways. We are beginning to understand how exogenous signals provided by oxygen and N oxides are processed for activating the underlying gene programs. Key signals are provided by nitrate, nitric oxide, and a low oxygen tension. In the genus Pseudomonas the nitrate signal is processed by a two component regulatory system which activates the nar operon encoding respiratory nitrate reductase. Nitric oxide is not only an essential respiratory substrate of the denitrifying cell but constitutes in nanomolar concentrations also a key signal for the expression of nitrite reductase and NO reductase which control cellular NO homeostasis. The signal pathway in the genera Pseudomonas, Paracoccus and Rhodobacter involves regulators of the FNR family of transcription factors, which cluster phylogenetically in a separate subgroup. In contrast, Ralstonia eutropha requires a sigma-54 dependent regulator of the NtrC family for the expression of its quinol-dependent NO reductase. Important questions are directed currently at the mechanism(s) of activation of these transcription factors by NO, and avoidance of crosstalk with FNR factors at target promoters operating with identical recognition motifs.

Base Sequence↗
PubMed1992

The three-dimensional structures of methanol dehydrogenase from two methylotrophic bacteria at 2.6-A resolution.

The structures of methanol dehydrogenase (MEDH) from two closely related methylotrophic bacteria, Methylophilus methylotrophus and W3A1, have been determined at 2.6-A resolution. The molecule, a quinoprotein of molecular mass of about 138 kDa, contains two heavy (H) and two light (L) subunits of unknown sequence and two molecules of noncovalently associated pyrroloquinoline quinone. The two enzymes crystallize isomorphously in space group P2(1) with one H2L2 heterotetramer in the asymmetric unit. The electron density map of the M. methylophilus enzyme was obtained by multiple isomorphous replacement with anomalous scattering and improved by solvent leveling and electron density averaging. For model building, the amino acid sequence of MEDH from Paracoccus denitrificans for the H subunit and from Methylobacterium extorquens AM1 for the L subunit were used to represent the unknown amino acid sequence. At the present time, 579 and 57 amino acid residues for the large and small subunits, respectively, have been fitted into the map. The phases for MEDH from M. methylophilus were used directly to analyze the W3A1 structure, and both structures were refined to R-factors (where R = sigma[Fo-Fc[/sigma Fo) of 0.277 and 0.266, respectively. The L subunit contains a long alpha-helix and an extended N-terminal segment, both lying on the molecular surface of the H subunit. The H subunit contains eight antiparallel beta-sheets, each consisting of four strands arranged topologically like the letter W. The eight Ws are arranged circularly, forming the main disc-shaped body of the subunit, with some short helices and loops connecting the consecutive Ws, as well as some excursions within and between some of the Ws. The pyrroloquinoline quinone prosthetic group is located in the central channel of the large subunit near the surface of the molecule. The topology of the eight-W folding unit is similar to those of the six- and seven-W folding units previously reported for three other proteins, neuraminidase, methylamine dehydrogenase, and galactose oxidase.

Alcohol Oxidoreductases↗
PubMed1992

Cytochrome aa3 of Rhodobacter sphaeroides as a model for mitochondrial cytochrome c oxidase. The coxII/coxIII operon codes for structural and assembly proteins homologous to those in yeast.

The coxII/coxIII operon of Rhodobacter sphaeroides cytochrome c oxidase has been sequenced and characterized by insertional inactivation/complementation analysis. The organization of the genes in this locus (coxII.orf1.orf3.coxIII) is the same as that of the equivalent operon of Paracoccus denitrificans (ctaC.ctaB.ctaG.ctaE), but unlike that of other bacteria whose cytochrome oxidase genes have been characterized so far. The predicted amino acid sequence homology with eukaryotic oxidases is also higher for Rb. sphaeroides (and P. denitrificans) than for other bacterial versions of the enzyme. The inactivation of coxII results in loss of the characteristic cytochrome oxidase spectrum from membranes of the mutant strain. Full recovery requires introduction into the bacterium of the complete operon containing coxII.orf1.orf3.coxIII; partial complementation yielding a spectrally altered enzyme is achieved with a plasmid containing coxII or coxII.orf1.orf3. These results indicate that the peptides ORF1, ORF3, and COXIII are all required for assembly of native cytochrome c oxidase, suggesting an oxidase-specific assembly or chaperonin function for the ORFs in Rb. sphaeroides similar to that observed for the homologous gene products in yeast, COX10 and COX11.

Amino Acid Sequence↗
PubMed2003

Evolution of the bacterial community during granules formation in denitrifying reactors followed by molecular, culture-independent techniques.

The microbial community in two acetate-fed denitrifying reactors, inoculated with methanogenic sludge, was monitored by 16S rDNA-based methods (SSCP and FISH). Both reactors converged to similar, stable communities. The predominant organisms belonged to the genera Thauera, Paracoccus and Denitrobacter, detected both by molecular and culture-based methods.

Bacteria↗
PubMed2004

Microbial community structure of membrane fouling film in an intermittently and continuously aerated submerged membrane bioreactor treating domestic wastewater.

There was an observable difference in microbial community structure between suspended microorganisms and membrane biofouling film in intermittently and continuously aerated SMBRs. The dominant quinone type of membrane biofouling film in an intermittently aerated SMBR was ubiquinone (UQs)-8, -10 followed by menaquinone (MKs)-8(H4) and -8(H2). But that of the continuously aerated SMBR was UQs-10, -8 followed by MKs-6 and -8(H4). The experimental results also showed that the conditions of an intermittently aerated SMBR may contribute to biofouling by Pseudomonas, Moraxella, Vibrio (quinone type UQ-8), Staphylococcus warneri (quinone type MK-7), Micrococcus sp. (quinone type MK-8(H2)) and Nocardia sp. (quinone type MK-8(H4)), but biofouling in a continuously aerated SMBR may be due to Paracoccus sp. (quinone type: UQ-10) and Flavobacterium species (quinone type: MK-6). The microbial diversities in the intermittently aerated SMBR were 10.9 and 9.4 for biofouling film and suspended microorganisms, respectively. For the continuously aerated SMBR, the results were 10.4 and 10.5 for biofouling film and suspended microorganisms, respectively.

Bacteria↗
PubMed1990

Complete amino acid sequence of the cytochrome subunit and amino-terminal sequence of the flavin subunit of flavocytochrome c (sulfide dehydrogenase) from Chlorobium thiosulfatophilum.

The complete amino acid sequence of the 86-residue heme subunit of flavocytochrome c (sulfide dehydrogenase) from the green phototrophic bacterium Chlorobium thiosulfatophilum strain Tassajara has been determined as follows: APEQSKSIPRGEILSLSCAGCHGTDGKSESIIPTIYGRSAEYIESALLDFKSGA- RPSTVMGRHAKGYSDEEIHQIAEYFGSLSTMNN. The subunit has a single heme-binding site near the N terminus, consisting of a pair of cysteine residues at positions 18 and 21. The out-of-plane ligands are apparently contributed by histidine 22 and methionine 60. The molecular weight including heme is 10,014. The heme subunit is apparently homologous to small cytochromes c by virtue of the location of the heme-binding site and its extraplanar ligands. However, the amino acid sequence is closer to Paracoccus sp. cytochrome c554(548) (37%) than it is to the heme subunit from Pseudomonas putida p-cresol methylhydroxylase flavocytochrome c (20%). The flavocytochrome c heme subunit is only 14% similar to the small cytochrome c555 also found in Chlorobium. Secondary structure predictions suggest N- and C-terminal helices as expected, but the midsection of the protein probably folds somewhat differently from the small cytochromes of known three-dimensional structure such as Pseudomonas cytochrome c551. Analyses of the residues near the exposed heme edges of the cytochrome subunits of P. putida and C. thiosulfatophilum flavocytochromes c (assuming homology to proteins of known structure) indicate that charged residues are not conserved, suggesting that electrostatic interactions are not involved in the association of the heme and flavin subunits. The N-terminal sequence of the flavoprotein subunit of flavocytochrome has also been determined. It shows no similarity to the comparable region of the p-cresol methylhydroxylase flavoprotein subunit from P. putida. The flavin-binding hexapeptide, isolated and sequenced earlier (Kenney, W. C., McIntire, W., and Yamanaka, T. (1977) Biochim. Biophys. Acta 483, 467-474), is situated at positions 40-46.

Amino Acid Sequence↗
PubMed1990

The kinetic and isotopic competence of nitric oxide as an intermediate in denitrification.

Rates of NO uptake by five denitrifying bacteria were estimated by NO-electrode and gas chromatography methods under conditions of rather low cell densities and [NOaq]. The rates so measured, VmaxNO, represent lower limits for the true value of that parameter, but nevertheless exceed Vmax for nitrite uptake, VmaxNi, by a factor of two typically. Previous estimates under suboptimal conditions had placed VmaxNO at 0.3-0.5 of VmaxNi (St. John, R. T., and Hollocher, T. C. (1977) J. Biol. Chem. 252, 212-218; Garber, E. A. E., and Hollocher, T.C. (1981) J. Biol. Chem. 256, 5459-5465). The steady-state [NOaq] during denitrification of nitrite by nitrate-grown cells was less than or equal to 1 microM. The above observations, taken with a recent direct estimate for the KmNO for NO uptake of 0.4 microM (Zafiriou, O. C., Hanley, Q. S., and Snyder, G. (1989) J. Biol. Chem. 264, 5694-5699), would allow NO to be a free intermediate between nitrite and N2O with steady-state concentrations of less than or equal to 0.4 microM. As the result of special conditions during cell growth or differential inhibition by azide, it was possible to establish systems that accumulated NO during denitrification of nitrite. In all such cases, VmaxNO less than VmaxNi, and the time required to reach the maximum [NOaq] corresponded closely to the time needed to exhaust the nitrite. A semiquantitative isotope experiment with Paracoccus denitrificans demonstrated the trapping of 15NO from 15NO2- in a pool of NOaq. A quantitative isotope method using low densities of the same bacterium showed that 15N from 15NO2- and 14N from NOg combine randomly to form N2O during the simultaneous denitrification of 15NO2- and NO. The result requires that the pathways from nitrite and NO share a common mononitrogen intermediate. Results to the contrary obtained at high cell densities (first two references cited above) are now believed to have been due to technical artifacts. The present results are consistent with the view that NO is under kinetic control as a free intermediate in denitrification and serve to remove previously imagined constraints on this view.

Bacteria↗
PubMed1985

Quantitative selection of denitrifying bacteria in continuous cultures and requirement for organic carbon. I. Starch.

A mixed population of bacteria from bottom sludge of nitrogen wastewater reservoir was incubated in continuous culture in medium containing 1000 mg nitrate nitrogen/l and starch. Maximal efficiency of denitrification was 5 mg N/l/h. Marked changes in participation of denitrifying bacteria (16-76%) among total number of bacteria was observed, this being dependent on the ratio of starch concentration (CS) to nitrogen concentration (CN) in the medium. The optimal CS/CN ratio ensuring highest participation of denitrifying bacteria was 3.2. The amount of starch required for the denitrification of a defined quantity of nitrogen is negatively correlated (r = -0.98) with the frequency of the occurrence of denitrifying bacteria (XD) and is: CS = (5.53-0.028XD) CN. The denitrifying bacteria in continuous culture were dominated, depending on CS/CN ratio and flow rate of medium, by Alcaligenes faecalis, Paracoccus denitrificans or Pseudomonas mendocina, that is species unable to hydrolyse starch.

Bacteria↗
PubMed1985

Spectroscopic and functional properties of subunit III-depleted cytochrome oxidase.

Beef heart cytochrome c oxidase has been depleted of subunit III by treatment with chymotrypsin. The removal of subunit III has been evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel fluorography of preparations of the oxidase labeled with [14C]dicyclohexylcarbodiimide prior to proteolysis. Removal of subunit III resulted in a perturbation of the visible spectrum of reduced cytochrome oxidase. Subunit III-depleted oxidase is spectroscopically very similar to the oxidase from Paracoccus denitrificans. When reconstituted into liposomes, the depleted enzyme still pumped protons in response to a pulse of reduced cytochrome c. The H+/e- stoichiometry averaged 0.5. Redox-linked proton translocation could be observed only when respiratory control ratios were higher than 3 and the reductant pulse was of a magnitude that allowed for no more than 5 turnovers of the oxidase.

Animals↗
PubMed1988

Trapping of nitric oxide produced during denitrification by extracellular hemoglobin.

A spectrophotometric method has been developed that uses extracellular hemoglobin (Hb) to trap nitric oxide (NO) released during denitrification as nitrosyl hemoglobin (HbNO). The rate of complexation of NO with Hb is about at the diffusion controlled limit for protein molecules and the product, HbNO, is essentially stable. Hb was added to an anaerobic bacterial suspension and denitrification was initiated with either KNO2 or KNO3. HbNO formation was observed for six species of denitrifying bacteria and showed isosbestic points at 544, 568, and 586 nm. Cellular NO production, presumably by nitrite reductase, was kinetically distinct from the much slower chemical reaction of Hb with KNO2 to form methemoglobin and HbNO. The rate of HbNO formation was proportional to cell density, essentially independent of pH from 6.8 to 7.4, nearly zero order in [Hb] and, at least with Paracoccus denitrificans, strongly inhibited by rotenone and antimycin A. The Cu chelator, diethyldithiocarbamate, had no effect on HbNO formation by Pa. denitrificans, but abolished that by Achromobacter cycloclastes which uses a Cu-containing nitrite reductase known to be inactivated by the chelator. HbNO formation did not occur with non-denitrifying bacteria. The stoichiometry at high [Hb] for conversion of Hb to HbNO was 1.3-1.8 KNO2 per Hb for Pa. denitrificans, Pseudomonas aeruginosa, and A. cycloclastes and about 3.4 for Pseudomonas stutzeri. The former range of values corresponds to a partition of about 2 N atoms in 3 toward trapping and 1 in 3 toward reduction on the pathway to N2. Nitrogen not trapped appeared largely as N2O in presence of acetylene. The results are consistent with a model in which NO is a freely diffusible intermediate between nitrite and N2O, providing that nitric oxide reductase is or nearly is a diffusion controlled enzyme.

Antimycin A↗
PubMed1985

[Microflora in swine slurry as a parameter in determining the efficiency of deodorizing treatment. I. Continuous and discontinuous aeration treatment].

Liquid manure from the pig, fresh and stored, was treated by continuous and discontinuous aeration. The purpose was to achieve a biologically stabilized and deodorized organic material. The samples which were aerated intermittently had good decomposition rates for nitrogen compounds and even so good deodorization effects. In spite of a minimum of dissolved oxygen of appr. 0.2 mg/l, good deodorization could be achieved by intermittent aeration for 23 days. Simultaneous processes of nitrification and denitrification were observed in optimal aerated manure similar to activated sludge processes. On the other hand, significant shifts on the microflora could be shown, whereby the main part of the biota consists in the gramnegative, non fermentative organisms. In non-deodorized liquid manure, members of the genus Bacillus advanced in their growth rates. In addition to Alcaligenes-Pseudomonas organisms, the group of nonfermentative cocci (e. g. Moraxella spp., Paracoccus spp.) dominated. Their growth development during the treatment agreed very well with the results of decomposition and deodorization. The existence of Bifidobacterium and of Aerococcus in aerated pig slurry was not ascribed before.

Air↗
PubMedDate not supplied

[Elimination of nitrous oxide by a combined bacterial culture].

The ability of bacteria to eliminate nitrous oxide (N2O) from a gaseous phase containing 20% O2 was studied. Representatives of the following physiological groups were found to be incapable of removing N2O: denitrifying bacteria (Paracoccus denitrificans), nitrifying bacteria (Nitrosospira briensis), carboxydobacteria (Pseudomonas carboxydoflava), methane oxidizing bacteria (Methylosinus trichosporium), and nitrogen fixing bacteria (Bacillus polymyxa). Five corynebacteria-like strains were isolated from soil samples actively eliminating N2O under oxidative conditions. None of the strains could remove considerable amounts of N2O in pure culture. The rate of N2O elimination was much higher than that of the initial cultures if a combined culture comprising five strains was used. Three strains of the combined culture formed H2O2 and possessed a low catalase activity whereas the remaining two did not produce H2O2 and decomposed hydrogen peroxide at a high rate; this suggests that the catalase mechanism is involved in the elimination of N2O.

Bacteria↗
PubMed1983

Effect of various sources of organic carbon and high nitrite and nitrate concentrations on the selection of denitrifying bacteria. II. Continuous cultures in packed bed reactors.

The effect of different organic compounds, nitrites and nitrates at the concentration of 1,000 mg N/l on the quantitative and strain-specific selection of denitrifying bacteria was determined in anaerobic packed bed reactors. Both the source of carbon and nitrogen form influenced strain specificity and the frequency of occurrence of denitrifying bacteria. The frequency of denitrifying bacteria within packed bed reactor ranged in different media from 11% (glucose and nitrates) to 100% (methanol and ethanol with nitrates). A single species selection was observed in the presence of nitrites within packed bed reactor: Pseudomonas aeruginosa in medium with acetate. Pseudomonas stutzeri in medium with ethanol, Pseudomonas mendocina in medium with methanol and Pseudomonas fluorescens in medium with glucose. When nitrates were present in packed bed reactor, the dominating bacteria were: P. stutzeri in medium with acetate, P. fluorescens in medium with ethanol, Paracoccus denitrificans in medium with methanol and Alcaligenes faecalis in medium with glucose.

Acetates↗
PubMed1983

15N-tracer and NMR studies on the pathway of denitrification. Evidence against trioxodinitrate but for nitroxyl as an intermediate.

The effects of four species of denitrifying bacteria on the conversion of [15N]nitrite to trioxodinitrate (HN2O3-) and N2O and of trioxodinitrate to N2O were studied. For all species, the N2O produced in the presence of [15N]nitrite and trioxodinitrate was isotopically randomized throughout the period of incubation and was not composed at the outset predominantly of 14N2O or 14N2O plus 15N2O. The N2O produced was also heavily enriched in 15N at times when the trioxodinitrate pool was only weakly enriched in 15N. By 15N NMR, the N(2) position, but not the N(1) position, of trioxodinitrate was found to become progressively labeled with 15N during incubation with [15N]nitrite. These results argue that (a) the N-N bond of trioxodinitrate is not preserved in its conversion to N2O, (b) trioxodinitrate can be neither a free nor enzyme-bound intermediate in denitrifying bacteria, and (c) the pathways from nitrite and trioxodinitrate involve a common mononitrogen intermediate. The conclusion that this intermediate is probably nitroxyl (HNO), at least with Paracoccus denitrificans and Pseudomonas stutzeri, provides indirect evidence that N-N bond formation in denitrification can occur through the dimerization of nitroxyl.

Isotope Labeling↗
PubMed1994

Cloning, sequence analysis, and expression of the genes encoding the two subunits of the methylotrophic bacterium W3A1 electron transfer flavoprotein.

The genes encoding the two different subunits of the electron transfer flavoprotein (ETF) from the methylotrophic bacterium W3A1 have been identified, cloned, and sequenced. A 0.8-kilobase pair DNA fragment was generated for use as a molecular probe by the amplification of genomic sequences using the polymerase chain reaction and a primer pair with degenerate sequences derived from the NH2-terminal amino acid sequences determined for the ETF subunits purified from W3A1. The screening of a partial genomic minilibrary containing size-selected BamHI-SalI fragments using this probe identified a 2.2-kilobase pair insert containing the complete coding sequences for both W3A1 ETF subunits. The genes are arranged in tandem in the genomic DNA with only 2 bases between the TAG translation termination codon of the small subunit and the ATG translation initiation codon of the large subunit. The deduced amino acid sequences of each of the W3A1 ETF subunits exhibit only approximately 30% identity with the corresponding subunits of the ETF from human, rat, and Paracoccus denitrificans, which as a group are greater than 50% identical. Thus, the ETF from W3A1 may exhibit some unique structural features that, like other differences in some of its physical and functional properties, may distinguish this ETF from others in this family. A highly homologous region near the COOH terminus of the large subunit in all the ETF proteins was found to contain a sequence that matches in several ways the ADP-binding motif of flavoproteins and other dinucleotide-binding proteins, suggesting that the large subunit forms a portion of the FAD (or AMP) binding site in these proteins. Under control of the tac promoter, the cloned ETF subunit genes were co-expressed in Escherichia coli producing the heterodimeric holoprotein with physical, spectral, and electron-accepting properties essentially identical to the ETF isolated from W3A1. The recombinant ETF serves as the electron acceptor for W3A1 trimethylamine dehydrogenase in vitro, accumulating as the air-stable anionic semiquinone in the presence of excess trimethylamine. Fully reduced ETF could not be obtained even after prolonged enzymatic reduction.

Amino Acid Sequence↗
PubMed1993

Characterization of a cta/CDE operon-like genomic region encoding subunits I-III of the cytochrome c oxidase of the cyanobacterium Synechocystis PCC 6803.

Strong heterologous hybridization of a synthetic oligonucleotide probe of 17 bp originally used to clone subunit I of the Paracoccus denitrificans cytochrome c oxidase (M. Raitio, T. Jalli and M. Saraste (1987) EMBO J. 6, 2825-2833) to a single band was observed on Southern blots of Anacystis nidulans R2 (Synechococcus PCC 7942), Synechocystis PCC 6803, and Nostoc Mac PCC 8002 chromosomal DNA digests. Six pooled gene banks prepared from Synechocystis PCC 6803 contained regions that hybridized to the oligonucleotide (probe C) which is specifically directed toward the putative Cu-binding site VWAHHMY of subunit I. Two of these gene banks were transformed into Escherichia coli and screened for colonies hybridizing to probe C. Several clones were recovered, and one type of plasmid was identified from each gene bank. The two (overlapping) plasmids were called pDAUV1 and pDAUV2. A restriction map of the plasmids showed that the overlapping region contained an 80 bp PvuI-KpnI fragment binding to probe C. The two clones together permitted sequencing of the entire gene for cytochrome c oxidase subunit I from Synechocystis PCC 6803. Further systematic sequencing of approximately 1000 bp upstream and downstream each of the ctaD (subunit I) gene revealed the presence of two genes encoding subunits II (ctaC gene) and III (ctaE gene) due to conspicuous similarities to homologous genes from other cytochrome c oxidase-containing organisms. Yet, no indications of genes encoding additional subunits of the oxidase were found within the region sequenced.

Amino Acid Sequence↗
PubMed1998

Pressure and temperature dependence of enantioselective excited-state quenching of chiral Tb(III) and Eu(III) tris(pyridine-2,6-dicarboxylate) chelates by various C-type ferricytochromes.

For mitochondrial ferricytochrome c from horse, cow and tuna and for bacterial cytochrome c-550 from Paracoccus versutus, the pressure and temperature dependence of their quenching of racemic Tb(DPA)3(3-) and Eu(DPA)3(3-) (DPA = pyridine-2,6-dicarboxylate) luminescence in aqueous solution is investigated. Of these energy transfer reactions the activation volumes (delta V#) and energies (Ea) are determined for the ranges P = 0-3 kbar and T = 15-40 degrees C. For the lambda enantiomers of Tb(DPA)3(3-) and Eu(DPA)3(3-), delta V# and Ea are almost the same for all proteins: 0.4 < or = delta V# < or = 1.1 cm3/mol and 0 < or = Ea < or = 2 kJ/mol. For the delta enantiomer, whose luminescence is quenched faster, the activation parameters vary significantly with the origin of the protein and they are different for Tb(DPA)3(3-) and Eu(DPA)3(3-). Values for delta V#, delta range from +4.9 +/- 0.5 (Eu/horse) to +0.5 +/- 0.5 cm3/mol (Tb/tuna); Ea ranges from +8 +/- 1 (Tb/cow) to -1 +/- 1 kj/mol (Tb/tuna). The degree of enantioselectivity in the quenching (Eq) by cytc from horse, cow, chicken and pigeon is almost the same and markedly higher than from tuna. The differing quenching characteristics of the tuna protein are ascribed to the amino acid variations near the exposed heme edge: Ile9-->Thr, Thr28-->Val and/or Phe46-->Tyr. Other variations in this region, Thr47-->Ser and Ala15-->Ser, do not affect Eq.

Amino Acid Sequence↗
PubMed2002

Recovery and separation of cell lysate proteins using hydrogels guided by aqueous two-phase extraction principles.

The addition of poly(ethylene glycol) and salts to clarified cell lysates of Thiosphaera pantotropha increases sorption of microbial proteins into dextran hydrogels, consistent with the thermodynamics of aqueous two-phase extraction. Addition of 12 wt% PEG-10,000 to the lysate increased total sorption of protein by the dextran gel from 5.2 mg/g dextran to 37 mg/g; addition of either 0.1 M potassium iodide or tetrabutylammonium fluoride along with PEG to the lysate increased protein sorption to more than 63 mg/g, a 12-fold increase. SDS-PAGE demonstrated that the type of salt added controls which proteins are absorbed by the gel. Previously demonstrated only with model solutions, these results suggest another approach to recovery and separation strategies for proteins produced by fermentation.

Absorption↗