Dissociation Constants of Cytochrome P450 2C9/Cytochrome P450 Reductase Complexes in a Lipid Bilayer Membrane Depend on NADPH: A Single-Protein Tracking Study

Single-Lipid Diffusion Behaviors in Cell Membranes Modulated by Cholesterol-Based Heterogeneity

Over a century after the proposal of Fluid Mosaic Model, the relationship between functionally related multiple-scale spatial heterogeneity of the cell membrane and mobility of component molecules, both inherent features of cell membrane, remains elusive. Single-lipid tracking enables the analysis of structural heterogeneity at different spatial scales within the cell membrane from a lipid diffusion perspective. Herein, specifically designed cholesterol (Chol)-based membrane systems were utilized to investigate the distinct impacts of molecular-level interactions between diverse membrane components and micrometer-scale spatial confinement on lipid diffusion. The results demonstrate that the incorporation of Chol into 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membranes decelerates lipid diffusion, with a positive correlation observed between the degree of deceleration and the mole ratio of Chol molecules. Across all these systems, lipid diffusion consistently adheres to the continuous time random walk (CTRW) model, indicating lipid entrapment resulting from specific molecular interactions. Conversely, micrometer-scale spatial confinement induced by phase separation not only reduces the diffusion rate of DOPC molecules but also triggers a transition from CTRW to fractional Brownian motion (fBM) or random walk on a fractal (RWF) mode within a confinement width range of 6.3-5.4 μm, suggesting a crowded microenvironment. In living cell membranes, this transformation in lipid diffusion is observed following Chol depletion, implying that lipid raft disruption leads to increased crowding within the lipid microenvironment. This study enhances our understanding of the relationship between lipid diffusion and membrane microenvironment across different spatial scales while providing insights into characterizing spatially heterogeneous structures within cell membranes from the perspective of lipid diffusion.

Leaflet-Specific Structure and Dynamics of Solid and Polymer Supported Lipid Bilayers

Polymer-supported or tethered lipid bilayers serve as versatile platforms for mimicking plasma membrane structure and dynamics, yet the impact of polymer supports on lipid bilayers remains largely unresolved. In this study, we introduce a novel methodology that combines graphene-induced energy transfer (GIET) with line-scan fluorescence lifetime correlation spectroscopy (lsFLCS) to examine the structural and dynamic properties of lipid bilayers. Our findings reveal that polymer supports markedly influence both the structural parameters, such as the membrane height from the substrate, its thickness, as well as dynamic properties, including leaflet-specific diffusion coefficients and interleaflet coupling. These findings highlight the complex interplay between a polymer support and the lipid bilayers. By resolving leaflet-specific diffusion and heights of the two leaflets from the substrate, this study emphasizes the potential of GIET-lsFLCS for probing membrane dynamics and structure. These insights significantly advance the understanding and application of polymer-supported membranes across diverse research contexts.

Tuning architectural organization of eukaryotic P450 system to boost bioproduction in Escherichia coli

Eukaryotic cytochrome P450 enzymes, generally colocalizing with their redox partner cytochrome P450 reductase (CPR) on the cytoplasmic surface of organelle membranes, often perform poorly in prokaryotic cells, whether expressed with CPR as a tandem chimera or free-floating individuals, causing a low titer of heterologous chemicals. To improve their biosynthetic performance in Escherichia coli, here, we architecturally design self-assembled alternatives of eukaryotic P450 system using reconstructed P450 and CPR, and create a set of N-termini-bridged P450-CPR heterodimers as the counterparts of eukaryotic P450 system with N-terminus-guided colocalization. The covalent counterparts show superior and robust biosynthetic performance, and the N-termini-bridged architecture is validated to improve the biosynthetic performance of both plant and human P450 systems. Furthermore, the architectural configuration of protein assemblies has an inherent effect on the biosynthetic performance of N-termini-bridged P450-CPR heterodimers. The results suggest that spatial architecture-guided protein assembly could serve as an efficient strategy for improving the biosynthetic performance of protein complexes, particularly those related to eukaryotic membranes, in prokaryotic and even eukaryotic hosts.

AMPK regulates phagophore-to-autophagosome maturation

Autophagy is an important metabolic pathway that can non-selectively recycle cellular material or lead to targeted degradation of protein aggregates or damaged organelles. Autophagosome formation starts with autophagy factors accumulating on lipid vesicles containing ATG9. These phagophores attach to donor membranes, expand via ATG2-mediated lipid transfer, capture cargo, and mature into autophagosomes, ultimately fusing with lysosomes for their degradation. Autophagy can be activated by nutrient stress, for example, by a reduction in the cellular levels of amino acids. In contrast, how autophagy is regulated by low cellular ATP levels via the AMP-activated protein kinase (AMPK), an important therapeutic target, is less clear. Using live-cell imaging and an automated image analysis pipeline, we systematically dissect how nutrient starvation regulates autophagosome biogenesis. We demonstrate that glucose starvation downregulates autophagosome maturation by AMPK-mediated inhibition of phagophore tethering to donor membrane. Our results clarify AMPKs regulatory role in autophagy and highlight its potential as a therapeutic target to reduce autophagy.

Structural insights into the semiquinone form of human Cytochrome P450 reductase by DEER distance measurements between a native flavin and a spin labelled non-canonical amino acid

The flavoprotein Cytochrome P450 reductase (CPR) is the unique electron pathway from NADPH to Cytochrome P450 (CYPs). The conformational dynamics of human CPR in solution, which involves transitions from a "locked/closed" to an "unlocked/open" state, is crucial for electron transfer. To date, however, the factors guiding these changes remain unknown. By Site-Directed Spin Labelling coupled to Electron Paramagnetic Resonance spectroscopy, we have incorporated a non-canonical amino acid onto the flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) domains of soluble human CPR, and labelled it with a specific nitroxide spin probe. Taking advantage of the endogenous FMN cofactor, we successfully measured for the first time, the distance distribution by DEER between the semiquinone state FMNH• and the nitroxide. The DEER data revealed a salt concentration-dependent distance distribution, evidence of an "open" CPR conformation at high salt concentrations exceeding previous reports. We also conducted molecular dynamics simulations which unveiled a diverse ensemble of conformations for the "open" semiquinone state of the CPR at high salt concentration. This study unravels the conformational landscape of the one electron reduced state of CPR, which had never been studied before.

High-Level De Novo Production of (2S)-Eriodictyol in Yarrowia Lipolytica by Metabolic Pathway and NADPH Regeneration Engineering

(2S)-Eriodictyol, a polyphenolic flavonoid, has found widespread applications in health supplements and food additives. However, the limited availability of plant-derived (2S)-eriodictyol cannot meet the market demand. Microbial production of (2S)-eriodictyol faces challenges, including the low catalytic efficiency of flavone 3'-hydroxylase/cytochrome P450 reductase (F3'H/CPR), insufficient precursor supplementation, and inadequate NADPH regeneration. This study systematically engineered Yarrowia lipolytica for high-level (2S)-eriodictyol production. In doing this, the expression of F3'H/CPR was balanced, and the supply of precursors was enhanced by relieving feedback inhibition of the shikimate pathway, promoting fatty acid β-oxidation, and increasing the copy number of synthetic pathway genes. These strategies, combined with NADPH regeneration, achieved an (2S)-eriodictyol titer of 423.6 mg/L. Finally, in fed-batch fermentation, a remarkable 6.8 g/L (2S)-eriodictyol was obtained, representing the highest de novo microbial titer reported to date and paving the way for industrial production.

Thermodynamics and S-Palmitoylation Dependence of Interactions between Human Aquaporin-4 M1 Tetramers in Model Membranes

Aquaporin-4 (AQP4) is a water channel protein found primarily in the central nervous system (CNS) that helps to regulate water-ion homeostasis. AQP4 exists in two major isoforms: M1 and M23. While both isoforms have a homotetrameric quaternary structure and are functionally identical when transporting water, the M23 isoform forms large protein aggregates known as orthogonal arrays of particles (OAPs). In contrast, the M1 isoform creates a peripheral layer around the outside of these OAPs, suggesting a thermodynamically stable interaction between the two. Structurally, the M1 isoform has an N-terminal tail that is 22 amino acids longer than the M23 isoform and contains two solvent-accessible cysteines available for S-palmitoylation at cysteine-13 (Cys-13) and cysteine-17 (Cys-17) in the amino acid sequence. Earlier work suggests that the palmitoylation of these cysteines might aid in regulating AQP4 assemblies. This work discusses the thermodynamic driving forces for M1 protein-protein interactions and how the palmitoylation state of M1 affects them. Using temperature-dependent single-particle tracking, the standard state free energies, enthalpies, and entropies were measured for these interactions. Furthermore, we present a binding model based on measured thermodynamics and a structural modeling study. The results of this study demonstrate that the M1 isoform will associate with itself according to the following expressions: 2[AQP4-M1]4 ↔ [[AQP4-M1]4]2 when palmitoylated and 3[AQP4-M1]4 ↔ [AQP4-M1]4 + [[AQP4-M1]4]2 ↔ [[AQP4-M1]4]3 when depalmitoylated. This is primarily due to a conformational change induced by adding the palmitic acid groups at Cys-13 and Cys-17 in the N-terminal tails of the homotetramers. In addition, a statistical mechanical model was developed to estimate the Gibbs free energy, enthalpy, and entropy for forming dimers and trimers. These results were in good agreement with experimental values.

AMPK Regulates Phagophore-to-Autophagosome Maturation

Autophagy is an important metabolic pathway that can non-selectively recycle cellular material or lead to targeted degradation of protein aggregates or damaged organelles. Autophagosome formation starts with autophagy factors accumulating on lipid vesicles containing ATG9. These phagophores attach to donor membranes, expand via ATG2-mediated lipid transfer, capture cargo, and mature into autophagosomes, ultimately fusing with lysosomes for their degradation. Autophagy can be activated by nutrient stress, for example by a reduction in the cellular levels of amino acids. In contrast, how autophagy is regulated by low cellular ATP levels via the AMP-activated protein kinase (AMPK), an important therapeutic target, is less clear. Using live-cell imaging and an automated image analysis pipeline, we systematically dissect how nutrient starvation regulates autophagosome biogenesis. We demonstrate that glucose starvation downregulates autophagosome maturation by AMPK mediated inhibition of phagophores tethering to donor membranes. Our results clarify AMPK's regulatory role in autophagy and highlight its potential as a therapeutic target to reduce autophagy.

Hybrid bilayer membranes as platforms for biomimicry and catalysis

Hybrid bilayer membrane (HBM) platforms represent an emerging nanoscale bio-inspired interface that has broad implications in energy catalysis and smart molecular devices. An HBM contains multiple modular components that include an underlying inorganic surface with a biological layer appended on top. The inorganic interface serves as a support with robust mechanical properties that can also be decorated with functional moieties, sensing units and catalytic active sites. The biological layer contains lipids and membrane-bound entities that facilitate or alter the activity and selectivity of the embedded functional motifs. With their structural complexity and functional flexibility, HBMs have been demonstrated to enhance catalytic turnover frequency and regulate product selectivity of the O₂ and CO₂ reduction reactions, which have applications in fuel cells and electrolysers. HBMs can also steer the mechanistic pathways of proton-coupled electron transfer (PCET) reactions of quinones and metal complexes by tuning electron and proton delivery rates. Beyond energy catalysis, HBMs have been equipped with enzyme mimics and membrane-bound redox agents to recapitulate natural energy transport chains. With channels and carriers incorporated, HBM sensors can quantify transmembrane events. This Review serves to summarize the major accomplishments achieved using HBMs in the past decade.

Engineering Saccharomyces cerevisiae for the production of dihydroquercetin from naringenin

Background

Dihydroquercetin (DHQ), a powerful bioflavonoid, has a number of health-promoting qualities and shows potential as a treatment for a number of disorders. Dihydroquercetin biosynthesis is a promising solution to meet the rising demand for dihydroquercetin. However, due to the significant accumulation of eriodietyol (ERI), naringenin (NAR), dihydrokaempferol (DHK), and other metabolites, the yield of DHQ biosynthesis is low. As a result, this is the hindrance to the biosynthesis of DHQ.

Results

In this study, we proposed several strategies to enhance the product formation and reduce the metabolites in accumulation. The flavonoid 3′-hydroxylase (F3′H) and cytochrome P450 reductase from different species were co-expressed in S. cerevisiae, and the best strain expressing the P450-reductase enzyme complex (SmF3′H/ScCPR) yielded 435.7 ± 7.6 mg/L of ERI from NAR in the deepwell microplate. The product conversion rate was improved further by mutating the predicted potential ubiquitination sites to improve SmF3′H stability, resulting in a 12.8% increase in titre using the mutant SmF3′H (K290R). Besides, different F3Hs from various sources and promoters were tested for the improved DHQ production, with the best strain producing 381.2 ± 10.7 mg/L of DHQ from 1 g/L of NAR, suggesting the temporal regulation the expression of F3H is important for maximization the function of F3′H and F3H.

Conclusion

This study offers effective strategies for improving DHQ production from NAR and could be used as a reference for related research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01937-8.

Thermodynamic Driving Forces of Redox-Dependent CPR Insertion into Biomimetic Endoplasmic Reticulum Membranes

Cytochrome P450 reductase (CPR) is a NADPH-dependent membrane-bound oxidoreductase found in the endoplasmic reticulum (ER) and is the main redox partner for most cytochrome P450 enzymes. Presented are the measured thermodynamic driving forces responsible for how strongly CPR partitions into a biomimetic ER with the same lipid composition of a natural ER. Using temperature-dependent fluorescence correlation spectroscopy and fluorescence single-protein tracking, the standard state free energies, enthalpies, and entropies of the CPR insertion process were all measured. The results of this study demonstrate that the thermodynamic driving forces are dependent on the redox states of CPR. In particular, the partitioning of CPR^ox into a biomimetic ER is an exothermic process with a small positive change in entropy, while CPR^red partitioning is endothermic with a large positive change in entropy. Both resulted in negative free energies and strong association to the biomimetic ER, but the K_P of CPR^ox insertion is measurably smaller than that of CPR^red. Using this new information and known results from literature sources, we also present a phenomenological model that accounts for membrane-protein interactions, protein orientation relative to the membrane, and protein conformation as a function of the redox state.

Membrane anchoring facilitates colocalization of enzymes in plant cytochrome P450 redox systems

Plant metabolism depends on cascade reactions mediated by dynamic enzyme assemblies known as metabolons. In this context, the cytochrome P450 (P450) superfamily catalyze key reactions underpinning the unique diversity of bioactive compounds. In contrast to their soluble bacterial counterparts, eukaryotic P450s are anchored to the endoplasmic reticulum membrane and serve as metabolon nucleation sites. Hence, membrane anchoring appears to play a pivotal role in the evolution of complex biosynthetic pathways. Here, a model membrane assay enabled characterization of membrane anchor dynamics by single molecule microscopy. As a model system, we reconstituted the membrane anchor of cytochrome P450 oxidoreductase (POR), the ubiquitous electron donor to all microsomal P450s. The transmembrane segment in the membrane anchor of POR is relatively conserved, corroborating its functional importance. We observe dynamic colocalization of the POR anchors in our assay suggesting that membrane anchoring might promote intermolecular interactions and in this way impact assembly of metabolic multienzyme complexes.

Structural Dynamics of Cytochrome P450 3A4 in the Presence of Substrates and Cytochrome P450 Reductase

Cytochrome P450 3A4 (CYP3A4) is the most important drug-metabolizing enzyme in humans and has been associated with harmful drug interactions. The activity of CYP3A4 is known to be modulated by several compounds and by the electron transfer partner, cytochrome P450 reductase (CPR). The underlying mechanism of these effects, however, is poorly understood. We have used hydrogen-deuterium exchange mass spectrometry to investigate the impact of binding of CPR and of three different substrates (7-benzyloxy-4-trifluoromethyl-coumarin, testosterone, and progesterone) on the conformational dynamics of CYP3A4. Here, we report that interaction of CYP3A4 with substrates or with the oxidized or reduced forms of CPR leads to a global rigidification of the CYP3A4 structure. This was evident from the suppression of deuterium exchange in several regions of CYP3A4, including regions known to be involved in protein-protein interactions (helix C) and substrate binding and specificity (helices B' and E, and loop K/β1). Furthermore, the bimodal isotopic distributions observed for some CYP3A4-derived peptides were drastically impacted upon binding to CPR and/or substrates, suggesting the existence of stable CYP3A4 conformational populations that are perturbed by ligand/CPR binding. The results have implications for understanding the mechanisms of ligand binding, allostery, and catalysis in CYP enzymes.

Biased cytochrome P450-mediated metabolism via small-molecule ligands binding P450 oxidoreductase

Metabolic control is mediated by the dynamic assemblies and function of multiple redox enzymes. A key element in these assemblies, the P450 oxidoreductase (POR), donates electrons and selectively activates numerous (>50 in humans and >300 in plants) cytochromes P450 (CYPs) controlling metabolism of drugs, steroids and xenobiotics in humans and natural product biosynthesis in plants. The mechanisms underlying POR-mediated CYP metabolism remain poorly understood and to date no ligand binding has been described to regulate the specificity of POR. Here, using a combination of computational modeling and functional assays, we identify ligands that dock on POR and bias its specificity towards CYP redox partners, across mammal and plant kingdom. Single molecule FRET studies reveal ligand binding to alter POR conformational sampling, which results in biased activation of metabolic cascades in whole cell assays. We propose the model of biased metabolism, a mechanism akin to biased signaling of GPCRs, where ligand binding on POR stabilizes different conformational states that are linked to distinct metabolic outcomes. Biased metabolism may allow designing pathway-specific therapeutics or personalized food suppressing undesired, disease-related, metabolic pathways.

Effector role of cytochrome P450 reductase for androstenedione binding to human aromatase

Cytochromes P450 constitute a large superfamily of monooxygenases involved in many metabolic pathways. Most of them are not self-sufficient and need a reductase protein to provide the electrons necessary for catalysis. It was shown that the redox partner plays a role in the modulation of the structure and function of some bacterial P450 enzymes. Here, the effect of NADPH-cytochrome reductase (CPR) on human aromatase (Aro) is studied for what concerns its role in substrate binding. Pre-steady-state kinetic experiments indicate that both the substrate binding rates and the percentage of spin shift detected for aromatase are increased when CPR is present. Moreover, aromatase binds the substrate through a conformational selection mechanism, suggesting a possible effector role of CPR. The thermodynamic parameters for the formation of the CPR-Aro complex were studied by isothermal titration calorimetry. The dissociation constant of the complex formation is 4.5 folds lower for substrate-free compared to the substrate-bound enzyme. The enthalpy change observed when the CPR-Aro complex forms in the absence of the substrate are higher than in its presence, indicating that more interactions are formed/broken in the former case. Taken together, our data confirm that CPR has a role in promoting aromatase conformation optimal for substrate binding.

A Guide to Tracking Single Membrane Proteins and Their Interactions in Supported Lipid Bilayers

The purpose of this chapter is to serve as a guide for those who wish to carry out experiments tracking single proteins in planar supported biomimetic membranes. This chapter describes, in detail, the construction of a simple single molecule microscope, which includes: (1) a parts list, (2) temperature control, (3) an alignment procedure, (4) a calibration procedure, and (5) a procedure for measuring the mechanical stability of the instrument. It also gives procedures for making planar supported bilayers on hydrophilically treated borosilicate and quartz. These include (1) POPC bilayers, (2) POPC/PEG-PE cushioned bilayers, (3) POPC/PEG-PE cushioned bilayers on BSA passivated substrates, and (4) a cushioned biomimetic membrane of the endoplasmic reticulum (ER). A procedure for the detergent mediated incorporation of the transmembrane protein 5HT_3A (a serotonin receptor) is also described and can be used as a starting point for other large non-self-inserting transmembrane proteins. A procedure for the detergent-free incorporation of cytochrome P450 reductase (CPR) and cytochrome P450 enzymes (P450) into an ER biomimetic is also described. The final experimental section of this chapter details different procedures for data analysis including (1) quantitative analysis of mean squared displacements from individually tracked proteins, (2) gamma distribution analysis of diffusion coefficients from a small ensemble of individually tracked proteins, (3) average mean squared displacement analysis, (4) Gaussian analysis of step-size distributions, (5) Arrhenius analysis of temperature dependent data, (6) the determination of equilibrium constants from a step-size distribution, and (7) a perspective associated with the interpretation of single particle tracking data.

Encapsulation of Flavin Cofactor within a Manganese Porphyrin-Based Metal-Organic Polyhedron for Reductive Dioxygen Activation

Encapsulation of flavin mononucleotide (FMN) in a porphyrinatomanganese(III)-based cubic cage allowed the fast reduction of manganese(III) porphyrin in the presence of nicotinamide adenine dinucleotide (NADH). This supramolecular system was capable of efficiently activating dioxygen and catalyzing the oxidation of benzyl alcohol. Control experiments suggested that the close proximity between FMN and manganese(III) porphyrins forced by the host-guest interaction might benefit the electron-transfer process from the FMN cofactor to the metal centers.

Coupling of Redox and Structural States in Cytochrome P450 Reductase Studied by Molecular Dynamics Simulation

Cytochrome P450 reductase (CPR) is the key protein that regulates the electron transfer from NADPH to various heme-containing monooxygenases. CPR has two flavin-containing domains: one with flavin adenine dinucleotide (FAD), called FAD domain, and the other with flavin mononucleotide (FMN), called FMN domain. It is considered that the electron transfer occurs via FAD and FMN (NADPH → FAD → FMN → monooxygenase) and is regulated by an interdomain open-close motion. It is generally thought that the structural state is coupled with the redox state, which, however, has not yet been firmly established. In this report, we studied the coupling of the redox and the structural states by full-scale molecular dynamics (MD) simulation of CPR (total 86.4 μs). Our MD result showed that while CPR predominantly adopts the closed state both in the oxidized and reduced states, it exhibits a tendency to open in the reduced state. We also found a correlation between the FAD-FMN distance and the predicted FMN-monooxygenase distance, which is embedded in the equilibrium thermal fluctuation of CPR. Based on these results, a physical mechanism for the electron transfer by CPR is discussed.

Post-Translational Regulation of CYP450s Metabolism As Revealed by All-Atoms Simulations of the Aromatase Enzyme

Phosphorylation by kinases enzymes is a widespread regulatory mechanism able of rapidly altering the function of target proteins. Among these are cytochrome P450s (CYP450), a superfamily of enzymes performing the oxidation of endogenous and exogenous substrates thanks to the electron supply of a redox partner. In spite of its pivotal role, the molecular mechanism by which phosphorylation modulates CYP450s metabolism remains elusive. Here by performing microsecond-long all-atom molecular dynamics simulations, we disclose how phosphorylation regulates estrogen biosynthesis, catalyzed by the Human Aromatase (HA) enzyme. Namely, we unprecedentedly propose that HA phosphorylation at Y361 markedly stabilizes its adduct with the flavin mononucleotide domain of CYP450s reductase (CPR), the redox partner of microsomal CYP450s, and a variety of other proteins. With CPR present at physiological conditions in a limiting ratio with respect to its multiple oxidative partners, the enhanced stability of the CPR/HA adduct may favor HA in the competition with the other proteins requiring CPR's electron supply, ultimately facilitating the electron transfer and estrogen biosynthesis. As a result, our work elucidates at atomic-level the post-translational regulation of CYP450s catalysis. Given the potential for rational clinical management of diseases associated with steroid metabolism disorders, unraveling this mechanism is of utmost importance, and raises the intriguing perspective of exploiting this knowledge to devise novel therapies.

Tripping the light fantastic in membrane redox biology: linking dynamic structures to function in ER electron transfer chains

How the dynamics of proteins assist catalysis is a contemporary issue in enzymology. In particular, this holds true for membrane‐bound enzymes, where multiple structural, spectroscopic and biochemical approaches are needed to build up a comprehensive picture of how dynamics influence enzyme reaction cycles. Of note are the recent studies of cytochrome P450 reductases (CPR)–P450 (CYP) endoplasmic reticulum redox chains, showing the relationship between dynamics and electron flow through flavin and haem redox centres and the impact this has on monooxygenation chemistry. These studies have led to deeper understanding of mechanisms of electron flow, including the timing and control of electron delivery to protein‐bound cofactors needed to facilitate CYP‐catalysed reactions. Individual and multiple component systems have been used to capture biochemical behaviour and these have led to the emergence of more integrated models of catalysis. Crucially, the effects of membrane environment and composition on reaction cycle chemistry have also been probed, including effects on coenzyme binding/release, thermodynamic control of electron transfer, conformational coupling between partner proteins and vectorial versus ‘off pathway’ electron flow. Here, we review these studies and discuss evidence for the emergence of dynamic structural models of electron flow along human microsomal CPR–P450 redox chains.

Lipid-exchange in nanodiscs discloses membrane boundaries of cytochrome-P450 reductase

Lipids are critical for the function of membrane proteins. NADPH-cytochrome-P450-reductase, the sole electron transferase for microsomal oxygenases, possesses a conformational dynamics entwined with its topology. Here, we use peptide-nanodiscs to unveil cytochrome-P450-reductase's lipid boundaries, demonstrating a protein-driven enrichment of ethanolamine lipids (by 25%) which ameliorates by 3-fold CPR's electron-transfer ability.

Cytochrome-P450-Induced Ordering of Microsomal Membranes Modulates Affinity for Drugs

Although membrane environment is known to boost drug metabolism by mammalian cytochrome P450s, the factors that stabilize the structural folding and enhance protein function are unclear. In this study, we use peptide-based lipid nanodiscs to "trap" the lipid boundaries of microsomal cytochrome P450 2B4. We report the first evidence that CYP2B4 is able to induce the formation of raft domains in a biomimetic compound of the endoplasmic reticulum. NMR experiments were used to identify and quantitatively determine the lipids present in nanodiscs. A combination of biophysical experiments and molecular dynamics simulations revealed a sphingomyelin binding region in CYP2B4. The protein-induced lipid raft formation increased the thermal stability of P450 and dramatically altered ligand binding kinetics of the hydrophilic ligand BHT. These results unveil membrane/protein dynamics that contribute to the delicate mechanism of redox catalysis in lipid membrane.