SPR and electrochemical analyses of interactions between CYP3A4 or 3A5 and cytochrome b5

[SPR analysis of protein-protein interactions with P450 cytochromes and cytochrome b5 integrated into lipid membrane]

Identification of new protein-protein interactions (PPI) and characterization of quantitative parameters of complex formation represent one of central tasks of protein interactomics. This work is a logical continuation of the cycle of our previous works devoted to the study of PPIs among the components of cytochrome P450-dependent monooxygenase system. Using an optical biosensor of Surface Plasmon Resonance (SPR biosensor), a comparative analysis on the determination of kinetic and equilibrium parameters of complex formation between the membrane-bound hemoprotein cytochrome b5 with cytochrome P450s was performed using two different protocols for protein immobilization: 1) covalent non-oriented one on to the carboxymethyl dextran chip type CM and 2) non-covalent oriented immobilization in the lipid environment on the chip type L1 with internal control of liposomes surface distribution. In the second protocol it was shown that the complex formation was characterized by 2.5 times higher affinity due to an decrease in rate dissociation constants. The appropriateness of using both experimental models is discussed.

SPR-Based study of affinity of cytochrome P450s / redox partners interactions modulated by steroidal substrates

The goal of this work was to test the hypothesis that the affinity of protein-protein interactions in the cytochrome P450-dependent monooxygenase system is modulated by the low-molecular-weight compounds (substrates or inhibitors). The surface plasmon resonance (SPR) based study was carried out using the recombinant protein preparations of three microsomal cytochromes P450 (CYP17A1, CYP21A2, and CYP2C19) and their redox partners: cytochrome b5 (CYB5A), NADPH - cytochrome P450 reductase (CPR), and also iron-sulfur protein adrenodoxin (Adx). As a result, we have revealed some specificity of the influence of the steroid substrates on the binding affinity of CYPs with their redox partners, namely: the lack of effect on CPR/CYPs and Adx/CYP complex formation, and a significant effect on interactions between CYB5A and steroidogenic CYPs. The equilibrium dissociation constant (Kd) value of the CYB5A/CYP17A1 complex decreased by 5 times in the presence of progesterone (P4), which was due to a 10 times increase in the association rate constant (k_on). In this case, a twofold increase in the dissociation rate constant (k_off) value of CYB5A/CYP17A1 complex formation was observed. It was also demonstrated that the affinity of CYB5A/CYP17A1 interaction increased in the presence of two other steroidal substrates 17α-hydroxyprogesterone and pregnenolone and that effect was comparable with P4. In contrast, only the twofold decrease in the affinity of CYB5A/CYP21A2 interaction in the presence of P4 was caused by a slight increase in the k_off value (the k_on value of the complex did not change). This indicates a different format of the steroidal substrates effects expressed in a change in the stability of the CYB5A/CYPs complexes. Thus, it was found that P4 modulated the both kinetic and equilibrium constants of CYB5A/CYP17A1 and CYB5/CYP21A2 complex formation and complexes, while not affecting the CYB5A/CYP2C19 interaction (2C19 is the cytochrome P450 isoenzyme possessing broad substrate specificity), thereby indicating a specific influence of steroidal substrates on interactions involving steroidogenic CYPs. Our results are consistent with current understanding of the role of CYB5A as a regulator of cytochrome P450 activity in P450-dependent monooxygenase system.

A New Method for Quantitative Determination of Steroid Metabolites of Cytochrome P450-Dependent Reactions Using Fluorescent Spectroscopy

A method for determination of hydroxylase activity of cytochrome P450 3A4 (CYP3A4) towards its substrate hydrocortisone using fluorescent analysis of the product was developed. 6β-hydroxycortisol, formed during CYP3A4-dependent electrocatalysis, has a characteristic fluorescent peak at λ = 427 ± 2 nm after treating with the sulfuric acid : ethanol (3 : 1) mixture and excitation at λ = 365 nm, which is different from the substrate (hydrocortisone) fluorescence (λ = 525 ± 2 nm). The limit of detection of 6β-hydroxycortisol was 0.32 μM. The developed analytical approach was used to determine the kinetic parameters of CYP3A4-dependent hydrocortisone hydroxylation.

Interaction of prostacyclin synthase with cytochromes P450

Biosensor experiments on investigation of interaction between prostacyclin synthase (PGIS) and different proteins of the cytochrome P450 monooxygenase systems were perfomed. Interaction of PGIS with microsomal (CYP21A2, CYP2E1) and mitochondrial (CYP27A1, CYP11B1, CYP11B2, CYP11A1) cytochrome P450s was detected. Kinetic and equilibrium parameters of protein complexes formation were determined. Data obtained suggest an essential role of these hemoproteins interaction in regulation of prostacyclin and thromboxane A2 biosynthesis.

From electrochemistry to enzyme kinetics of cytochrome P450

This review is an attempt to describe advancements in the electrochemistry of cytochrome P450 enzymes (EC 1.14.14.1) and to study molecular aspects and catalytic behavior of enzymatic electrocatalysis. Electroanalysis of cytochrome P450 demonstrates how to translate theoretical laws and equations of classical electrochemistry for the calculation of the kinetic parameters of enzymatic reactions and then translation of kinetic parameters to interpretation of drug-drug interactions. The functional significance of cytochrome P450s (CYPs) includes the metabolism of drugs, foreign chemicals, and endogenic compounds. The pharmaceutical industry needs sensitive and cost-effective systems for screening new drugs and investigation of drug-drug interactions. The development of different types of CYP-based biosensors is now in great demand. This review also highlights the characteristics of electrode processes and electrode properties for optimization of the cytochrome P450 electroanalysis. Electrochemical cytochrome P450-biosensors are the most studied. In this review, we analyzed electrode/cytochrome P450 systems in terms of the mechanisms underlying P450-catalyzed reactions. Screening of potential substrates or inhibitors of cytochromes P450 by means of electrodes were described.

[Methods for determining of cytochrome P450 isozymes functional activity]

The review is dedicated to modern methods and technologies for determining of cytochrome P450 isozymes functional activity, such as absorbance and fluorescent spectroscopy, electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), Raman, Mossbauer, and X-ray spectroscopy, surface plasmon resonance (SPR), atomic force microscopy (AFM). Methods of molecular genetic analysis were reviewed from personalized medicine point of view. The use of chromate-mass-spectrometric methods for cytochrome P450-dependent catalytic reactions' products was discussed. The review covers modern electrochemical systems based on cytochrome P450 isozymes for their catalytic activity analysis, their use in practice and further development perspectives for experimental pharmacology, biotechnology and translational medicine.

[The analysis of participation of individual proteins in the protein interactome formation]

It becomes increasingly clear that most proteins of living systems exist as components of various protein complexes rather than individual molecules. The use of various proteomic techniques significantly extended our knowledge not only about functioning of individual complexes but also formed a basis for systemic analysis of protein-protein interactions. In this study gel-filtration chromatography accompanied by mass-spectrometry was used for the interactome analysis of human liver proteins. In six fractions (with average molecular masses of 45 kDa, 60 kDa, 85 kDa, 150 kDa, 250 kDa, and 440 kDa) 797 proteins were identified. In dependence of their distribution profiles in the fractions, these proteins could be subdivided into four groups: (1) single monomeric proteins that are not involved in formation of stable protein complexes; (2) proteins existing as homodimers or heterodimers with comparable partners; (3) proteins that are partially exist as monomers and partially as components of protein complexes; (4) proteins that do not exist in the monomolecular state, but also exist within protein complexes containing three or more subunits. Application of this approach to known isatin-binding proteins resulted in identification of proteins involved in formation of the homo- and heterodimers and mixed protein complexes.

[Study specificity of isatin interactions with P450 cytochromes]

Cytochrome P450-dependent monooxygenase systems exist basically in all living organisms, where they perform various important functions. The coordinated functioning of these systems involves many proteins participating in different protein-protein interactions (PPI). Previously, we have found that the endogenous non-peptide bioregulator isatin (indoledione-2,3), synthesized from indole by means of certain cytochromes P450 (e.g. P450 2E1, P450 2C19, P450 2A6) regulates affinity of some PPI. In this work, an attempt has been undertaken to register a direct interaction of isatin with a set of different proteins related to the functioning of cytochrome P450-dependent monooxygenase: five isoforms of cytochromes P450, two isoforms of cytochrome b5, cytochrome P450 reductase, adrenodoxin, adrenodoxin reductase and ferrochelatase. The study has shown that isatin binds specifically only to cytochromes P450 with high affinity (the equilibrium dissociation constant (Kd) is about 10-8 M).

The effect of isatin on protein-protein interactions between cytochrome b5 and cytochromes P450

Cytochromes P450 (CYP) are involved in numerous biochemical processes including metabolism of xenobiotics, biosynthesis of cholesterol, steroid hormones etc. Since some CYP catalyze indol oxidation to isatin, we have hypothesized that isatin can regulate protein-protein interactions (PPI) between components of the CYP system thus representing a (negative?) feedback mechanism. The aim of this study was to investigate a possible effect of isatin on interaction of human CYP with cytochrome b5 (CYB5A). Using the optical biosensor test system employing surface plasmon resonance (SPR) we have investigated interaction of immobilized CYB5A with various CYP in the absence and in the presence of isatin. The SPR-based experiments have shown that a high concentration of isatin (270 mM) increases Kd values for complexes CYB5A/CYP3А5 and CYB5A/CYP3A4 (twofold and threefold, respectively), but has no influence on complex formation between CYB5A and other CYP (including indol-metabolizing CYP2C19 and CYP2E1). Isatin injection to the optical biosensor chip with the preformed molecular complex CYB5A/CYP3A4 caused a 30%-increase in its dissociation rate. Molecular docking manipulations have shown that isatin can influence interaction of CYP3А5 or CYP3A4 with CYB5A acting at the contact region of CYB5A/CYP.

Scrutiny of electrochemically-driven electrocatalysis of C-19 steroid 1α-hydroxylase (CYP260A1) from Sorangium cellulosum So ce56

Direct electrochemistry and bioelectrocatalysis of a newly discovered C-19 steroid 1α-hydroxylase (CYP260A1) from the myxobacterium Sorangium cellulosum So ce56 were investigated. CYP260A1 was immobilized on screen-printed graphite electrodes (SPE) modified with gold nanoparticles, stabilized by didodecyldimethylammonium bromide (SPE/DDAB/Au). Cyclic voltammograms in argon-saturated substrate free 0.1 M potassium phosphate buffer, pH 7.4, and in enzyme-substrate complex with androstenedione demonstrated a redox processes with a single redox couple of E(0') of -299 ± 16 mV and -297.5 ± 21 mV (vs. Ag/AgCl), respectively. CYP260A1 exhibited an electrocatalytic activity detected by an increase of the reduction current in the presence of dissolved oxygen and upon addition of the substrate (androstenedione) in the air-saturated buffer. The catalytic current of the enzyme correlated with substrate concentration in the electrochemical system and this dependence can be described by electrochemical Michaelis-Menten model. The products of CYP260A1-depended electrolysis at controlled working electrode potential of androstenedione were analyzed by mass-spectrometry. MS analysis revealed a mono-hydroxylated product of CYP260A1-dependent electrocatalytic reaction towards androstenedione.

[Optical surface plasmon resonance biosensors in molecular fishing]

An optical biosensor employing surface plasmon resonance is a highly efficient instrument applicable for direct real time registration of molecular interactions without additional use of any labels or coupled processes. As an independent approach it is especially effective in analysis of various ligand receptor interactions. SPR-biosensors are used for validation of studies on intermolecular interactions in complex biological systems (affinity profiling of various groups of proteins, etc.). Recently, potential application of the SPR-biosensor for molecular fishing (direct affinity binding of target molecules from complex biological mixtures on the optical biosensor surface followed by their elution for identification by LC-MS/MS) has been demonstrated. Using SPR-biosensors in such studies it is possible to solve the following tasks: (a) SPR-based selection of immobilization conditions required for the most effective affinity separation of a particular biological sample; (b) SPR-based molecular fishing for subsequent protein identification by mass spectrometry; (c) SPR-based validation of the interaction of identified proteins with immobilized ligand. This review considers practical application of the SPR technology in the context of recent studies performed in the Institute of Biomedical Chemistry on molecular fishing of real biological objects.

[Electrochemical methods for biomedical investigations]

In the review, authors discussed recently published experimental data concerning highly sensitive electrochemical methods and technologies for biomedical investigations in the postgenomic era. Developments in electrochemical biosensors systems for the analysis of various bio objects are also considered: cytochrome P450s, cardiac markers, bacterial cells, the analysis of proteins based on electro oxidized amino acids as a tool for analysis of conformational events. The electroanalysis of catalytic activity of cytochromes P450 allowed developing system for screening of potential substrates, inhibitors or modulators of catalytic functions of this class of hemoproteins. The highly sensitive quartz crystal microbalance (QCM) immunosensor has been developed for analysis of bio affinity interactions of antibodies with troponin I in plasma. The QCM technique allowed real-time monitoring of the kinetic differences in specific interactions and nonspecific sorption, with out multiple labeling procedures and separation steps. The affinity binding process was characterized by the association (ka) and the dissociation (kd) kinetic constants and the equilibrium association (K) constant, calculated using experimental data. Based on the electroactivity of bacterial cells, the electrochemical system for determination of sensitivity of the microbial cells to antibiotics cefepime, ampicillin, amikacin, and erythromycin was proposed. It was shown that the minimally detectable cell number corresponds to 106 CFU per electrode. The electrochemical method allows estimating the degree of E.coli JM109 cells resistance to antibiotics within 2-5 h. Electrosynthesis of polymeric analogs of antibodies for myoglobin (molecularly imprinted polymer, MIP) on the surface of graphite screen-printed electrodes as sensor elements with o- phenylenediamine as the functional monomer was developed. Molecularly imprinted polymers demonstrate selective complementary binding of a template protein molecule (myoglobin) by the "key-lock" principle.

Electrocatalytic cycle of P450 cytochromes: the protective and stimulating roles of antioxidants

This study reports the investigation of the catalytic activity of isolated cytochromes from the cytochrome P450 superfamily. Electrochemically driven CYP reactions may have practical relevance, providing a useful tool for drug assay studies.