Bicarbonate Binding Research Articles

CORRELATION BETWEEN THE BINDING OF FORMATE AND DECREASED RATES OF CHARGE TRANSFER THROUGH THE PHOTOSYSTEM II QUINONES

Abstract— The binding parameters of bicarbonate to the thylakoid membrane at different formate concentrations have been established [Stemler and Murphy (1983) Photochem. Phorobiol. 38, 701–707]. Based on these parameters, predictions could be made concerning the effects of bicarbonate and formate on photosynthetic electron flow. In this work these effects of various concentrations of bicarbonate and formate are measured and compared to predictions from the binding study. Electron flow is measured between QA and QB (the primary and secondary quinone acceptors) and QB and the plastoquinone pool. Also, these same concentration effects are determined for silicomolybdate supported oxygen evolution. It is found that the results of the bicarbonate binding study are in good agreement with the concentration dependence determined for the quinone reactions, as well as the silicomolybdate reaction. The bicarbonate concentrations required for half‐maximal effects are approximately 100 μM, 300 μM and 1.3 mM in the presence of 0, 20 mM and 100 mM formate, respectively. It is concluded that a hierarchy of possible electron flow rates exist. The slowest rates occur when formate is bound. A substantially higher rate occurs when neither formate nor bicarbonate (< 2 μM) are present, but only chloride is present. The highest rates of electron flow occur when bicarbonate is bound. The QA‐ QB→ Qa Qb− Qa− Qb2– PQ → Qa Qb‐ PQ2–, and the silicomolybdate reactions all have the same concentration dependence on formate and bicarbonate. From this it is concluded that a single binding site for formate and bicarbonate affect all of these reactions. The possibility that multiple sites exist with approximately equal affinities for bicarbonate cannot be excluded.

Electrostatic binding of bicarbonate and formate in viologen-based redox polymers: importance in catalytic reduction of bicarbonate to formate

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectrostatic binding of bicarbonate and formate in viologen-based redox polymers: importance in catalytic reduction of bicarbonate to formateJean Francois Andre and Mark S. WrightonCite this: Inorg. Chem. 1985, 24, 25, 4288–4292Publication Date (Print):December 1, 1985Publication History Published online1 May 2002Published inissue 1 December 1985https://doi.org/10.1021/ic00219a018RIGHTS & PERMISSIONSArticle Views107Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (531 KB) Get e-Alerts Get e-Alerts

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

Simultaneous binding of calcium and bicarbonate by conchiolin of oyster shells

Conchiolin of oyster shells selectively binds Ca2+. Bicarbonate is also bound but can be displaced by phosphate and sulfate. Conchiolin can be extracted to yield individual proteins with very high apparent molecular weights.

Kinetics of the reactivation of the Hill reaction in CO2‐depleted chloroplasts by addition of bicarbonate in the absence and in the presence of herbicides

In isolated broken chloroplasts photosynthetic electron transport requires the presence of CO2 and/or bicarbonate. This bicarbonate effect on electron flow was measured in a medium containing 100 mM sodium formate. In this medium a dark incubation time with bicarbonate is required for the reactivation of the Hill reaction. We have measured the kinetics of the reactivation of electron flow by varying the dark incubation of CO2‐depIeted pea (Pisum sativum L., cv. Rondo) chloroplasts with bicarbonate. The half‐time of this reactivation appears to be 25 s when 2 mM bicarbonate is added.The dinitrophenol herbicide, i‐dinoseb, is shown to be a competitive inhibitor of the bicarbonate dependent Hill reaction with an inhibitor constant (Ki) of 31 nM. In the presence of 100 nM i‐dinoseb or 100 nM DCMU the half‐time of the reactivation by 2 mM bicarbonate appears to increase to about 58 s. We provide an explanation for these phenomena by analyzing the bicarbonate‐thylakoid interaction on the basis of a simple reaction scheme. The binding of bicarbonate to the thylakoids appears to be a second order reaction with pseudo‐first order kinetics. According to our analysis, any inhibitor, which is competitive with respect to the bicarbonate stimulation of the Hill reaction, should increase the half‐time of the reactivation of the Hill reaction.

The apparent suppression of Na/K data obtained with ion-selective electrodes is due to junction potential and activity coefficient effects, not bicarbonate binding.

Journal Article The apparent suppression of Na/K data obtained with ion-selective electrodes is due to junction potential and activity coefficient effects, not bicarbonate binding. Get access J D Czaban, J D Czaban Search for other works by this author on: Oxford Academic Google Scholar A D Cormier, A D Cormier Search for other works by this author on: Oxford Academic Google Scholar K D Legg K D Legg Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 28, Issue 7, 1 July 1982, Pages 1703–1705, https://doi.org/10.1093/clinchem/28.7.1703 Published: 01 July 1982

In Reply: The Apparent Suppression of Na/K Data Obtained with Ion-Selective Electrodes Is Due to Junction Potential and Activity Coefficient Effects, Not Bicarbonate Binding

Journal Article In Reply: The Apparent Suppression of Na/K Data Obtained with Ion-Selective Electrodes Is Due to Junction Potential and Activity Coefficient Effects, Not Bicarbonate Binding Get access Robert L Coleman, Robert L Coleman NOVA Biomed. Corp. 20 Ossipee Rd. Newton, MA 02164 Search for other works by this author on: Oxford Academic Google Scholar C C Young C C Young NOVA Biomed. Corp. 20 Ossipee Rd. Newton, MA 02164 Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 28, Issue 7, 1 July 1982, Pages 1705–1706, https://doi.org/10.1093/clinchem/28.7.1705 Published: 01 July 1982

Analysis of bicarbonate binding to crocodilian hemoglobin.

Crocodilian hemoglobin has a high intrinsic oxygen affinity but does not react with those organic phosphate esters that normally control the oxygen affinity of blood in higher vertebrates. Instead, its oxygen affinity is greatly lowered by CO2. The present study was undertaken to determine the nature of the CO2 binding to the hemoglobin of a crocodilian species, the Caiman, both qualitatively and quantitatively. The following parameters were measured: (a) carbamino compounds of deoxy- and oxyhemoglobin, (b) the effect of CO2 (at constant pH) on the oxygen affinity of Caiman hemoglobin, (c) total CO2 concentration of hemoglobin solutions at different pH and pCO2 values, and (d) the effect of CO2 on CD spectra of Caiman aquomethemoglobin. An analysis of the results of these measurements revealed that CO2 binding in the form of carbamate was not oxygen-linked and cannot, therefore, mediate the CO2 effect on the oxygen affinity. It was found, however, that 2 mol of bicarbonate can be bound/hemoglobin tetramer and that the association constant of the bicarbonate anion greatly depends upon the state of ligation. At pH 7.02 and 25 degrees C, a numerical value of 2.0 X 10(3) M-1 was obtained for deoxyhemoglobin, while for oxyhemoglobin no significant bicarbonate binding could be observed. At more alkaline pH (pH greater than or equal to 7.5), the association constant for deoxyhemoglobin decreases. Circular dichroism of Caiman aquomethemoglobin decreased considerably in the 287-nm region upon addition of CO2 at constant pH, an effect very similar to the one caused by inositol hexaphosphate in human aquomethemoglobin.

Electrostatic effects in hemoglobin: electrostatic energy associated with allosteric transition and effector binding.

The pH dependence of the summed electrostatic stabilization for deoxy- and liganded hemoglobin was computed for several ionic strength values. The computed contribution to the stabilization of deoxyhemoglobin by binding of 2,3-diphosphoglycerate in the beta cleft compared well with experimental binding behavior for human hemoglobin A0 and hemoglobin F. The contribution of diphosphoglycerate binding to the alkaline Bohr effect was computed correctly for both hemoglobins A0 and F. The computed effects of simultaneous binding of diphosphoglycerate and formation of Val-1 beta carbamino adducts suggested a competition between these effectors. A direct competition was formulated between these two effectors, with extension to include a simple anion such as chloride or bicarbonate binding in competition with diphosphoglycerate but not with Val-1 beta carbamino formation. This model was found to hold at pH 7.3-7.4 over a range of concentrations of the effectors involved and to predict the pH dependence of Val-1 beta carbamino formation over the pH range 7.0-8.0. The pH dependence of the computed differential stability of liganded vs. unliganded hemoglobin A compared well with observation.

Action of bicarbonate and Photosystem 2 inhibiting herbicides on electron transport in pea grana and in thylakoids of a blue‐green alga

Bicarbonate (or carbon dioxide) is required for electron transport in isolated broken pea chloroplasts. The site of action of the bicarbonate ion is between the primary electron acceptor of Photosystem 2, Q, and the plastoquinone pool. After trypsin treatment the Hill reaction with ferricyanide does not require bicarbonate. Photosystem 2 inhibiting herbicides act also at this site. Therefore, a possible interaction of bicarbonate and these herbicides in their effect on photosynthetic electron transport was studied.The reciprocal of the Hill reaction rate in CO2‐depleted chloroplasts was plotted against the reciprocal of added bicarbonate concentration in the absence and in the presence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), 2‐methoxy‐4,6‐bis (ethylamino)‐1,3,5‐triazine (simeton) or 4,6‐dinitro‐o‐cresol (DNOC). From these Lineweaver‐Burk plots we concluded that DCMU and simeton inhibit both bicarbonate binding and Vmax. There is a purely competitive inhibition of bicarbonate binding by DNOC. We suggest that DNOC may exert its inhibition of electron transport by removing bicarbonate from its binding site.In isolated thylakoid membranes of Synechococcus leopoliensis we did not find a bicarbonate effect nor inhibition by DNOC after Q, indicating that in the thylakoids of this blue‐green alga the binding site for bicarbonate and DNOC between Q and plastoquinone is absent.

34] Rapid-rate equilibrium analysis of the interactions between organic phosphates and hemoglobins

This chapter discusses the rapid-rate equilibrium analysis of the interactions between organic phosphates and hemoglobins. The linkage relationships between the binding of protons, organic phosphate, chloride, bicarbonate, and oxygen to hemoglobin are well documented. While the major organic phosphate in mammalian erythrocytes is 2,3-diphosphoglycerate (DPG), different organic phosphates are employed by other species. This chapter also presents the general principle of the method. The method involves the use of a dialysis cell with an upper chamber, containing the macromolecule and radioactive ligand, separated by a suitable membrane from a lower chamber. Buffer is pumped through the lower chamber at a constant rate, and the effluent is collected and sampled for radioactivity measurements. The equilibrium concentration of free ligand can be measured by determining the rate of dialysis of the radioactive ligand across the membrane. The chapter presents the preparation and characterization of hemoglobin.

Glutamine-dependent carbamyl phosphate synthetase: catalysis and regulation

Glutamine-dependent carbamyl phosphate synthetase: catalysis and regulation

Inhibition of carbamyl phosphate synthetase by P1, P5-di(adenosine 5')-pentaphosphate: evidence for two ATP binding sites.

Studies on the effect of a series of alpha, omega-diadenosine 5'-polyphosphate (ApnA; n = 2 to 6) on carbamyl phosphate synthetase showed that only Ap5A is an effective inhibitor. Ap5A also inhibits two partial reactions catalyzed by the enzyme: bicarbonate-dependent ATPase and ATP synthesis from carbamyl phosphate and ADP. The data indicate that Ap5A binds to the enzyme sites that interact with ATP. Of a variety of ATP-utilizing enzymes (kinases, hydrolases, synthetases), only adenylate kinase (Leinhard, G. E., and Secemski, I. I. (1973) J. Biol. Chem. 248, 1121--1123) and carbamyl phosphate synthetase are inhibited by Ap5A. The present findings provide strong evidence that carbamyl phosphate synthetase has two separate binding sites for ATP in which the gamma-phosphate moeities of ATP are bound in close proximity to the bicarbonate binding site of the enzyme.

Adenosine triphosphatase from rat liver mitochondria — Evidence for a mercurial-sensitive site for the activating anion bicarbonate

The ATPase activity of purified mitochondrial ATPase (F 1) of rat liver is inhibited less than 15% by sulfhydryl reagents when assayed in TrisCl buffer. In Trisbicarbonate buffer the ATPase activity of the enzyme is two- to three-fold higher than in TrisCl. Significantly, the ATPase activity stimulated by bicarbonate can be inhibited by mercurial agents such as p-chloromercuribenzoate. The number of sulfhydryl groups accessible to 14C-p-chloromercuribenzoate is the same in TrisCl and Trisbicarbonate buffers. These experiments suggest that mercurials most likely inhibit bicarbonate-stimulated ATPase activity by blocking a site associated with bicarbonate binding rather than by blocking distinct sulfhydryl-sensitive hydrolytic sites induced by bicarbonate.

Fe(III) and Cu(II) conalbumin visible circular dichroism spectra

The single polypeptide chain of conalbumin strongly binds two Fe(III) or two Cu(II) ions to yield intense absorption in the visible region similar to that shown by the related protein transferrin. Comparison of the metal-ion-binding sites in the two proteins is made by exploiting the sensitivity to ligand geometry of circular dichroism (CD). For the Fe(III) proteins strong similarities of the CD spectra outweigh marginal differences. For Cu(II) conalbumin an additional negative extremum near 506 nm appears between two positive ones at 634 and 410 nm suggesting greater subtraction of oppositely signed CD components leading to lesser magnitudes for the two positive peaks than are found in Cu(II)-transferrin. The two Fe(III)-binding sites within conalbumin are compared by noting the strong similarities of the CD and MCD of proteins with Fe(III) in one site and Ga(III) in the other site, and vice versa, with the protein containing Fe(III) in both sites. Due to features of the amino acid sequences of the single protein chains, the four strong metal ion binding sites in conalbumin and transferrin cannot be identical in all particulars, yet CD spectra of their metal ion complexes are closely similar. From a study of model phenolate complexes and the wavelength maxima of visible absorption in the Fe(III), Cu(II), and Co(III) proteins near 465, 440, and 405 nm, respectively, these strong absorption bands are identified as ligand to metal ion electron-transfer transitions. It is suggested that tyrosyl residues are the donors in the electron transfer transitions and that they lock in the metal ions after being keyed into position by binding of bicarbonate or other anions.

The resonance Raman spectrum of the metalloprotein ovotransferrin.

Using ovotransferrin it is shown that amino-acid side chains forming the metal binding site in coloured metalloproteins can be identified and monitored by resonance Raman spectroscopy. All major features above 800 cm−1 in the resonance Raman spectrum of iron–bicarbonate ovotransferrin could be assigned to histidine or tyrosine vibrational modes, by comparison with Raman and infrared data for these amino acids and related compounds. Comparison of the features due to ring modes of imidazole ligated to Fe3+ in ovotransferrin with those of aqueous histidine at pH 8.0 suggests that rearrangement of the ring π electrons takes place upon ligation. Although iron–bicarbonate and iron–oxalate ovotransferrin have similar visible absorption spectra, differences in their resonance Raman spectra are clearly distinguishable, but no evidence was found for the direct binding of bicarbonate or oxalate to the iron. Differences between the geometries of the two sites at which iron is bound in iron–bicarbonate ovotransferrin appeared to be small compared with the perturbation caused to these sites by replacing bicarbonate with oxalate.

Nuclear Magnetic Relaxation Dispersion in Protein Solutions: III. COPPER TRANSFERRIN AND BICARBONATE-FREE COPPER TRANSFERRIN

Abstract To investigate the role of specifically bound bicarbonate in the metal-complexing function of transferrin, copper transferrin was prepared both in the presence and absence of bicarbonate ion. The magnetic field and temperature dependence of the solvent proton spin-lattice relaxation rate of solutions of the two complexes were determined. The molar relaxivity R (essentially, relaxation rate per protein concentration) for solutions of copper transferrin is very large at low fields (∼20,000 m-1 sec-1 at 4 Oe) and is highly field-dependent, decreasing to almost zero at 12 kOe. At low field, R is almost temperature-independent over the range 0–45°. Comparison of the results with theory indicates that protons are relaxed by a dipolar interaction with the unpaired electronic spin of Cu2+. The observed relaxivity results from the rapid exchange of a water molecule bound sufficiently close to the copper to be an axial ligand. The magnitude of R at low field for copper transferrin-HCO3 is about one-quarter of that for copper transferrin and also disperses almost to zero at high field. Above 25° the low field value of R has a strong positive temperature dependence. There is no significant variation in R over the pH range 7 to 9.5. The data suggest that, as in the absence of bicarbonate, the protons of water molecules are relaxed by a dipolar interaction with the electron spin of Cu2+, and that bicarbonate binding alters the water exchange rate.

Some specific interations of small ions with transferrin.

The fully iron saturated complex of transferrin was reconstituted from the apoprotein in the absence of bicarbonate but in the presence of other small anions. Bicarbonate was not found to be essential for the specific iron binding of the protein. The absorbance of the various complexes at 465 mμ was found to vary for each anion used to replace bicarbonate The simulataneous uptake of ferric iron and bicarbonate by apotransferrin was studied by equilibrium dialysis. The mean number of ferric ions bound per protein molecule was two. One bicarbonate ion was associated with each of the specifically bound ferric ions. Competitive binding experiments, in which other small anions displaced the bound bicarbonate, showed that oxalate was the strongest competitor for union with the bound iron. An oxalate ferric transferrin complex was prepared with the same stoichiometry as the bicarbonate complex. The optical rotatory dispersion properties of these complexes were compared in the visible-near ultraviolet region. The displacement of bicarbonate from the bicarbonate-ferric-transferrin complex, by oxalate, and the converse reaction, using oxalate-ferric-transferrin, were studied. Equilibrium equations are proposed for these reactions and the equilibrium constants calculated. The anomalous results obtained are discussed in terms of the mode of binding of bicarbonate and oxalate.

The activity of bovine carbonic anhydrase in imidazole buffers

Abstract The variation of activity with substrate concentration has been measured for bovine carbonic anhydrase (carbonate hydro-lyase, EC 4.2.1.1) at several hydrogen-ion concentrations between pH 6.2 and pH 7.7 in imidazole buffers containing a constant concentration of 1 anion. A simple kinetic picture emerges. In the hydration reaction K m does not vary between pH 6.7 and pH 7.7. ν max varies as if dependent on the ionisation of one group with a p K near 6.9, only the basic form being active. In the dehydration reaction in the range pH 6.2–7.45 the rate is proportional to the bicarbonate concentration: there is thus no apparent substrate binding. The rate varies with pH as though it depends on the ionisation of one group with p K near 6.9 only the acid form being active. The kinetic parameters for hydration and dehydration reactions obey the requirement for a reversible enzyme reaction throughout the range of hydrogen-ion concentration in which measurements on both reactions were made. It is suggested that the apparent binding of bicarbonate as substrate reported by other workers was due to an anionic inhibition of the enzyme by this ion in the dilute phosphate buffers they employed.