Spectrophotometric detection of the interaction between cytochrome c and heparin

High Immobilization Efficiency of Basic Protein within Heparin-Immobilized Calcium Phosphate Nanoparticles

Previously, we achieved one-pot fabrication of heparin-immobilized calcium phosphate (CaP) nanoparticles with high dispersibility by a precipitation process in a highly supersaturated reaction solution. In this study, we revealed that the heparin-immobilized CaP nanoparticles have a greater co-immobilizing capacity for basic proteins than for acidic proteins. In this process, heparin acted as not only a particle-dispersing agent but also as an immobilizing agent for basic proteins; it remarkably (approximately three-fold) improved the immobilization efficiency of cytochrome C (a model basic protein) within the CaP nanoparticles. The content of cytochrome C immobilized within the nanoparticles was increased with an increase in cytochrome C concentration in the reaction solution and by aging the nanoparticles. The obtained nanoparticles were dispersed well in water owing to their large negative zeta potentials derived from heparin, irrespective of the content of cytochrome C. Similar results were obtained also for another basic protein, lysozyme, but not for an acidic protein, albumin; the immobilization efficiency of albumin within the nanoparticles was decreased by heparin. These findings provide new insights into the co-immobilization strategy of proteins within heparin-immobilized CaP nanoparticles and will be useful in the design and fabrication of nanocarriers for protein delivery applications.

Superoxide dismutase 1 and glutathione peroxidase 1 are involved in the protective effect of sulodexide on vascular endothelial cells exposed to oxygen-glucose deprivation

Sulodexide (SDX) is widely used in the treatment of both arterial and venous thrombotic disorders. In addition to its recognized antithrombotic action, SDX has endothelial protective potential, which is independent of the coagulation/fibrinolysis system. However, the detailed molecular mechanisms of the endothelioprotective action of the drug are still unresolved. The aim of the present study was to determine whether treatment with SDX at concentrations of 0.125-0.5 lipase releasing unit (LRU)/ml have on the expression and activity of antioxidant enzymes in ischemic endothelial cells and how these effects might be related to the antiapoptotic properties of SDX. In the present study, human umbilical vein endothelial cells (HUVECs) were subjected to ischemia-simulating conditions (combined oxygen and glucose deprivation, OGD) for 6h to determine the protective effects of SDX. SDX (0.25 and 0.5LRU/ml) in OGD significantly increased the cell viability and prevented mitochondrial depolarization in the HUVECs. Moreover, SDX protected the HUVECs against OGD-induced apoptosis. At concentrations of 0.25 and 0.5LRU/ml, the drug increased both superoxide dismutase 1 (SOD1) and glutathione peroxidase 1 (GPx1) mRNA/protein expression together with a significant attenuation of oxidative stress in ischemic HUVECs. Our findings also demonstrate that an increase in both SOD and GPx activity is involved in the protective effect of SDX on ischemic endothelial cells. Altogether, these results suggest that SDX has a positive effect on ischemia-induced endothelial damage because of its antioxidant and antiapoptotic properties.

Dual effect of heparin on Fe²⁺-induced cardiolipin peroxidation: implications for peroxidation of cytochrome c oxidase bound cardiolipin

The effect of heparin on peroxidation of cardiolipin (CL) initiated by ferrous iron was studied in vitro using detergent-solubilized CL, liposomal CL, or CL bound to isolated cytochrome c oxidase (CcO). Heparin increased both the rate and the extent of CL peroxidation for detergent-solubilized CL and for CcO-bound CL. The effect of heparin was time- and concentration-dependent as monitored by the formation of conjugated dienes or thiobarbituric acid reactive substances. The results showed great similarity between the effect of heparin and the effect of certain iron chelators, such as ADP, on phospholipid peroxidation. Heparin increased the peroxidation of CcO-bound CL only when tertiary butyl hydroperoxide was also present. The enzyme activity of the resulting CcO complex decreased 25 %, in part due to peroxidation of functionally important CL. In contrast to peroxidation of detergent-solubilized CL, peroxidation of liposomal CL was inhibited by heparin, suggesting that the effect of heparin and ferrous iron depends on their proximity to the acyl chains of CL.

Interaction of cytochrome c with zinc oxide nanoparticles

The influence of pH on the interaction between horse heart ferricytochrome c (cyt c) and zinc oxide nanoparticles (ZnO NPs) has been studied by a small angle scattering as well as UV-vis and FTIR spectroscopy. The observations showed that the optimal pH for the association of protein with nanoparticles is in pH range 5.0-8.0. Almost no significant change in structure and thermodynamic stability of cytochrome c after the association with 60 nm ZnO NPs was performed by UV-vis and by a circular dichroism spectroscopy.

The anti-inflammatory effects of heparin and related compounds

Heparin is a glycosaminoglycan well known for its anticoagulant properties. In addition, heparin possesses anti-inflammatory effects. Although the mechanisms responsible for the anticoagulant effects of heparin are well understood, those underlying its anti-inflammatory effects are not. This review presents some of the evidence from clinical and animal studies supporting an anti-inflammatory role for heparin and heparin-related derivatives. Potential mechanisms by which heparin can exert its anti-inflammatory effects are discussed. The clinical use of heparin as an anti-inflammatory agent has been held back by the fear of bleeding. Development of nonanticoagulant heparins or heparin derivatives should mitigate this concern.

Resonance Raman investigations of cytochrome c conformational change upon interaction with the membranes of intact and Ca2+-exposed mitochondria

The conformational states of cytochrome c inside intact and Ca(2+)-exposed mitochondria have been investigated using resonance Raman spectroscopy. Intact and swelling bovine heart and rat liver mitochondria were examined with an excitation wavelength (413.1 nm) in resonance with the Soret transition of ferrous cytochrome c. The different b- to c-type cytochrome concentration ratio in mitochondria from two different tissues was used to help assign the Raman spectral components. Resonance Raman spectra were also recorded for mitochondria fractions (supernatants and pellets) obtained from swollen (Ca(2+)-exposed) mitochondria after differential centrifugation. The results illustrate that cytochrome c has an altered vibrational spectrum in solution, in intact, and in swollen mitochondria. When cytochrome c is released from mitochondria, its Raman spectrum becomes identical to that of ferrous cytochrome c in solution. The spectra of mitochondrial pellets indicate that a small amount of structurally modified cytochrome c remains associated with the heavy membrane fraction. Indeed, spectroscopic shifts in the low-frequency fingerprint and the high-frequency marker-band regions suggest that membrane binding leads to a partial opening of the heme pocket and an alteration of the heme thioether bonds. The results support the conclusion that most cytochrome c molecules in mitochondria are membrane-bound and that the cytochrome c structure changes upon binding. Furthermore, changes in the resonance Raman active mode located at 675 cm(-)(1) in the spectra of intact, swollen, and fractionated mitochondria indicate that b-type cytochromes may also undergo structural alterations during mitochondrial swelling and disruption.

Molten globule-like state of cytochrome c induced by polyanion poly(vinylsulfate) in slightly acidic pH

The effect of polyanion, poly(vinylsulfate), used as a model of negatively charged surface, on ferric cytochrome c (ferricyt c) structure in acidic pH has been studied by absorbance spectroscopy, circular dichroism (CD), tryptophan (Trp) fluorescence and microcalorimetry. The polyanion induced only small changes in the native structure of the protein at neutral pH, but it profoundly shifted the acid induced high spin state of the heme in the active center of cyt c to a more neutral pH region. Cooperativity of the acidic transition of ferricyt c in the presence of the polyanion was disturbed, in comparison with uncomplexed protein, as followed from different apparent pK(a) values observed in a distinct regions of the ferricyt c electronic absorbance spectrum (4.55+/-0.08 in the 620 nm band region and 5.47+/-0.15 in the Soret region). The ferricyt c structure in the complex with the polyanion at acidic pH (below pH 5.0) has properties of a molten globule-like state. Its tertiary structure is strongly disturbed according to CD and microcalorimetry measurements; however, its secondary structure, from CD, is still native-like and ferricyt c is in a compact state as evidenced by quenched Trp fluorescence. These findings are discussed in the context of the molten globule state of proteins induced on a negatively charged membrane surface under physiological conditions.

The structural and functional role of lysine residues in the binding domain of cytochrome c in the electron transfer to cytochrome c oxidase

The interactions of yeast iso-1 cytochrome c with bovine cytochrome c oxidase were studied using cytochrome c variants in which lysines of the binding domain were substituted by alanines. Resonance Raman spectra of the fully oxidized complexes of both proteins reveal structural changes of both the heme c and the hemes a and a3. The structural changes in cytochrome c are the same as those observed upon binding to phospholipid vesicles where the bound protein exists in two conformers, B1 and B2. Whereas the structure of B1 is the same as that of the unbound cytochrome c, the formation of B2 is associated with substantial alterations of the heme pocket. In cytochrome c oxidase, the structural changes in both hemes refer to more subtle perturbations of the immediate protein environment and may be a result of a conformational equilibrium involving two states. These changes are qualitatively different to those observed for cytochrome c oxidase upon poly-l-lysine binding. The resonance Raman spectra of the various cytochrome c/cytochrome c oxidase complexes were analyzed quantitatively. The spectroscopic studies were paralleled by steady-state kinetic measurements of the same protein combinations. The results of the spectra analysis and the kinetic studies were used to determine the stability of the complexes and the conformational equilibria B2/B1 for all cytochrome c variants. The complex stability decreases in the order: wild-type WT > J72K > K79A > K73A > K87A > J72A > K86A > K73A/K79A (where J is the natural trimethyl lysine). This order is not exhibited by the conformational equilibria. The electrostatic control of state B2 formation does not depend on individual intermolecular salt bridges, but on the charge distribution in a specific region of the front surface of cytochrome c that is defined by the lysyl residues at positions 72, 73 and 79. On the other hand, the conformational changes in cytochrome c oxidase were found to be independent of the identity of the bound cytochrome c variant. The maximum rate constants determined from steady-state kinetic measurements could be related to the conformational equilibria of the bound cytochrome c using a simple model that assumes that the conformational transitions are faster than product formation. Within this model, the data analysis leads to the conclusion that the interprotein electron transfer rate constant is around two times higher in state B2 than in B1. These results can be interpreted in terms of an increase of the driving force in state B2 as a result of the large negative shift of the reduction potential.

Coulombic and noncoulombic effect of polyanions on cytochrome c structure

The properties of the complexes of ferricytochrome c with two different polyanions--poly(vinylsulfate) and poly(4-styrene-sulfonate)--with a comparable charge density but with the different size of the uncharged part of their molecules have been studied by means of optical spectroscopy, differential scanning colorimetry, and gel chromatography. Ferriccytochrome c formed a complex with the former one through coulombic interactions and remained in a native-like state. The addition of the second polyanion to a solution of ferric cytochrome c at a low ionic strength, pH 7.0, resulted in profound conformational change in the hydrophobic core of protein (opening of the heme crevice with a perturbation of the methionine 80-heme iron bond and the hydrophobic core of the protein). These may be understood as an involvement of noncoulombic (hydrophobic, H-bonding) interactions of the uncharged part of the polyanion molecule. Conformational changes and the observed shift in acidic transition from low spin to high spin state of ferric cytochrome c detected in the presence of the polyanions may have biological implication in understanding the origin of conformational changes in proteins induced in the course of their interaction with membrane lipids and membrane proteins.

Structural and functional modifications of bovine trypsin by heparins. Influence of heparin molecular mass and structure

Heparins with different structures, charge density and molecular mass were evaluated for their capacity to induce structural and functional alterations of bovine trypsin in a low ionic strength buffer (20 mM Tris-HCl pH 7.4). Unfractionated heparin, and slow and fast moving heparin species increased the fluorescence peak emission of trypsin to the same extent (about +40.0%), whilst partially desulfated and re-N-acetylated heparin with a charge density of 1.47 modified the fluorescence at 330 nm by about +27% and natural heparan sulfate with a sulfate-to-carboxyl ratio < 1 by about +13%. Heparin fractions with narrow polydispersity and the same charge density (produced by chemical depolymerization in the presence of free radicals and further gel-permeation chromatography) having molecular mass lower than about 6000 interact with trypsin to a less extent, even though fractions with molecular mass of about 4500 and 3600 partially retain this property. No modification of fluorescence peak emission of trypsin with heparin was appreciable when the ionic strength of the buffer was increased to 0.3 mM NaCl. An altered ability to reduce cytochrome c was observed for heparins of different charge density; fragments with molecular mass lower than approximately 4000 were also unable to produce superoxide. Trypsin was degraded into fragments by heparin and derivatives after 3 h incubation at 37 degrees C. After electrophoresis in polyacrylamide-gels the trypsin bands disappeared and fragments with lower molecular mass were more evident. This effect depended on the molecular mass of heparin, and was more evident for unfractionated heparin and for a heparin fraction with a molecular mass of 7820. The esterolytic activity of trypsin was inhibited to the same extent by heparin derivatives of various structure and charge density while activity undermet minor changes in the presence of heparin fractions of Mr lower than 4000.

Interaction of alkaline phosphatase with cytochrome c

Alkaline phosphatase (AP) a protein which exhibits long-lived phosphorescence lifetime and ferricytochrome c as a phosphorescence quenching agent were examined. The excitation of the tryptophan triplet state resulted in cytochrome c reduction confirming long-range electron transfer as the quenching mechanism. The rate of electron transfer was not related to the length of the illumination interval; an additional reaction between the two proteins leading to cytochrome c reduction was detected. The reaction which proceeded in the dark was not sensitive to oxygen, was dependent on pH, and on the AP to cytochrome c ratio. At optimum 68 +/- 4% of the total cytochrome c could be reduced due to the presence of AP. On incubation of the two proteins the conformation of cytochrome c was altered as was evidenced by its decreased reducibility by ascorbate, by the disappearance of the absorption band at 695 nm, by the appearance of the new band at 620-640 nm, and by a change in circular dichroism spectra witnessing a structural alteration in the vicinity of the heme cleft. This was characterized by a profound increase in positive elipticity at 400 nm and by a reversible change in the magnitude of negative elipticity at 417 nm. The reaction was not significantly affected by the addition of sulfhydryl-binding and metal-complexing agents.

Studies on cytochrome c-heparin interactions by differential scanning calorimetry

The effects of heparin on the thermotropic properties of ferricytochrome c have been studied using high-sensitivity differential scanning calorimetry. Saturating concentrations of heparin at low ionic strength induced an important shift of the transition temperature Tm from 84.1 degrees C to 59.8 degrees C. This was accompanied by unusually large cooperativity of thermal denaturation of this complex, indicating strong intermolecular interactions between protein molecules. The destabilization of cytochrome c when mixed with heparin was not observed at high ionic strength, under which conditions complex was not formed.