Recombinant Pectobacterium carotovorum subsp. carotovorum Sulfoxide reductase heme-binding subunit YedZ (yedZ)

What is the YedZ protein and what is its function in Pectobacterium carotovorum?

YedZ (also known as Flavocytochrome YedZ) is a sulfoxide reductase heme-binding subunit found in Pectobacterium carotovorum subsp. carotovorum. This membrane-bound protein functions as part of electron transport systems involved in sulfoxide reduction. The protein contains a heme-binding domain that facilitates electron transfer during the reduction of sulfoxide compounds.

YedZ has the UniProt accession number C6DIK6 in P. carotovorum subsp. carotovorum (strain PC1) and is encoded by the yedZ gene (PC1_0246 locus) . The protein consists of 199 amino acids and appears to play a role in the bacterial response to environmental conditions, potentially contributing to pathogenicity or stress adaptation.

How does P. carotovorum YedZ compare structurally to YedZ proteins from other bacterial species?

While specific structural comparison data for P. carotovorum YedZ with other bacterial species is not directly provided in the search results, general protein analysis suggests significant structural similarities with YedZ homologs from related Enterobacteriaceae.

As a membrane-bound heme protein, P. carotovorum YedZ likely shares the conserved heme-binding domains found in other bacterial YedZ proteins. Like other YedZ proteins, it is characterized by multiple transmembrane regions, as evidenced by the hydrophobic amino acid stretches in its sequence . Comparative structural analysis would typically involve sequence alignment methods, hydropathy profiling, and possibly structural prediction algorithms to identify conserved domains across bacterial species.

What are the optimal conditions for expressing recombinant P. carotovorum YedZ in bacterial expression systems?

For optimal expression of recombinant P. carotovorum YedZ, researchers should consider the following methodological approaches:

• Expression System Selection: An E. coli expression system with a T7 promoter (such as BL21(DE3)) is typically effective for membrane proteins like YedZ.

• Temperature Optimization: Lower induction temperatures (16-20°C) often yield better results for membrane proteins by reducing aggregation and inclusion body formation.

• Induction Parameters: IPTG concentration should be optimized (typically 0.1-0.5 mM) with induction performed at mid-log phase (OD600 of 0.6-0.8).

• Media Supplementation: Addition of δ-aminolevulinic acid (0.5 mM) can enhance heme incorporation into the recombinant protein.

• Expression Vector Selection: Vectors containing fusion tags (such as His6, MBP, or SUMO) can improve solubility and facilitate purification.

For membrane proteins like YedZ, detergent screening is critical during purification to maintain protein stability and functionality. Commonly used detergents include n-dodecyl-β-D-maltoside (DDM), CHAPS, or Triton X-100.

What purification strategies are most effective for isolating recombinant YedZ while maintaining protein functionality?

A multi-step purification protocol is recommended for isolating functional recombinant YedZ:

• Membrane Fraction Isolation:

  • Harvest cells by centrifugation (6,000 × g, 15 min, 4°C)

  • Resuspend in buffer (typically 50 mM Tris-HCl pH 8.0, 200 mM NaCl)

  • Disrupt cells by sonication or French press

  • Remove cell debris by centrifugation (10,000 × g, 20 min, 4°C)

  • Isolate membrane fraction by ultracentrifugation (100,000 × g, 1 hour, 4°C)

• Solubilization and Affinity Purification:

  • Solubilize membrane fraction in buffer containing 1% DDM (or optimized detergent)

  • Apply to appropriate affinity resin (Ni-NTA for His-tagged constructs)

  • Wash extensively with buffer containing 0.05% DDM

  • Elute with imidazole gradient for His-tagged proteins

• Size Exclusion Chromatography:

  • Further purify using gel filtration (Superdex 200) in buffer with 0.02% DDM

  • Collect fractions containing YedZ

• Storage Considerations:

  • Store in Tris-based buffer with 50% glycerol at -20°C

  • For extended storage, store at -80°C

  • Avoid repeated freeze-thaw cycles

Throughout all purification steps, maintaining a reducing environment with agents like DTT or β-mercaptoethanol (1-5 mM) helps preserve the heme-binding functionality.

How can researchers verify the heme-binding functionality of purified recombinant YedZ?

To verify the heme-binding functionality of purified recombinant YedZ, researchers should employ multiple complementary techniques:

• UV-Visible Spectroscopy:

  • Scan purified protein from 250-700 nm

  • Look for characteristic Soret band (typically around 410-420 nm)

  • Compare oxidized vs. reduced spectra using sodium dithionite as reductant

  • The presence of α and β bands in the reduced spectrum (550-560 nm region) confirms heme incorporation

• Pyridine Hemochromogen Assay:

  • Mix protein with pyridine and sodium hydroxide

  • Record spectrum before and after reduction

  • Calculate heme content using extinction coefficients

• Electron Paramagnetic Resonance (EPR) Spectroscopy:

  • Analyze the oxidation state and coordination environment of the heme

  • Compare spectra with known heme-containing proteins

• Functional Enzyme Assays:

  • Measure sulfoxide reductase activity using model substrates (e.g., methionine sulfoxide)

  • Monitor activity spectrophotometrically using electron donors like NADH with appropriate mediators

A combination of these techniques provides comprehensive verification of heme incorporation and functional integrity of the purified YedZ protein.

How can researchers use site-directed mutagenesis to identify critical residues in YedZ function?

For researchers investigating structure-function relationships of YedZ through site-directed mutagenesis, the following methodological approach is recommended:

• Target Residue Selection:

  • Identify highly conserved residues through multiple sequence alignment with YedZ homologs

  • Focus on potential heme-coordination residues (typically His, Met, Cys)

  • Target transmembrane residues that might participate in electron transfer

  • Consider the conserved histidine residues and aromatic amino acids in membrane regions

• Mutagenesis Strategy:

  • Design primers for QuikChange or overlap extension PCR methods

  • Create conservative substitutions (e.g., His→Ala, His→Asn) to disrupt heme coordination

  • Introduce Cys→Ser mutations to evaluate disulfide participation

  • Consider introducing spectroscopic probes (e.g., Trp) at strategic positions

• Functional Characterization:

  • Compare wild-type and mutant proteins using:

    • UV-visible spectroscopy to assess heme incorporation

    • Enzyme kinetics to measure changes in catalytic efficiency

    • Protein stability assays to evaluate structural integrity

    • EPR spectroscopy to detect changes in heme environment

• Data Analysis Framework:

  • Create a classification system for mutations (e.g., "heme coordination," "electron transfer," "structural integrity")

  • Quantify the impact of each mutation on enzymatic parameters (kcat, KM)

  • Correlate spectroscopic changes with functional alterations

This systematic approach allows researchers to develop a comprehensive model of YedZ structure-function relationships.

What methods can be used to investigate YedZ interaction with other components of the bacterial electron transport chain?

To investigate YedZ interactions with other electron transport components, researchers should employ these complementary methodologies:

• Co-Immunoprecipitation (Co-IP):

  • Generate antibodies against YedZ or use epitope tags

  • Solubilize membrane fractions with mild detergents

  • Perform pull-down experiments and identify interacting partners by mass spectrometry

• Bacterial Two-Hybrid Analysis:

  • Create fusion constructs of YedZ and potential partners

  • Screen for protein-protein interactions in reporter strains

  • Confirm positive interactions with deletion constructs to map interaction domains

• Crosslinking Studies:

  • Use chemical crosslinkers of varying arm lengths

  • Apply photo-activatable crosslinkers for spatial precision

  • Analyze crosslinked complexes by SDS-PAGE and mass spectrometry

• Förster Resonance Energy Transfer (FRET):

  • Generate fluorescent protein fusions (e.g., YedZ-CFP)

  • Co-express with potential partners fused to acceptor fluorophores

  • Measure FRET efficiency in live cells or membrane vesicles

• Reconstitution Experiments:

  • Purify YedZ and potential partner proteins

  • Reconstitute into liposomes or nanodiscs

  • Measure electron transfer rates between components

• Differential In-vivo Crosslinking:

These approaches provide a comprehensive understanding of YedZ's role in electron transport pathways and identify its direct interaction partners.

How does YedZ contribute to P. carotovorum pathogenicity in plant infection models?

Investigating YedZ's role in P. carotovorum pathogenicity requires a multifaceted approach combining genetics, biochemistry, and plant infection models:

• Gene Knockout Studies:

  • Create ΔyedZ deletion mutants using homologous recombination or CRISPR-Cas9

  • Characterize growth phenotypes under various conditions

  • Compare virulence between wild-type and ΔyedZ strains in plant models

• Complementation Analysis:

  • Reintroduce wild-type yedZ on plasmids

  • Express site-directed mutants affecting heme-binding

  • Quantify restoration of phenotypes to confirm specificity

• Plant Infection Models:

  • Potato tuber slice assay: measure maceration zone diameters

  • Whole plant assays: quantify disease progression in stems/leaves

  • Microscopy to track bacterial invasion and plant tissue response

• Transcriptomic Analysis:

  • RNA-Seq comparison of wild-type vs. ΔyedZ during infection

  • Identify differentially expressed virulence genes

  • Map YedZ-dependent gene expression networks

• Metabolomic Profiling:

  • Analyze changes in bacterial and plant metabolites

  • Focus on redox-related compounds and sulfur-containing metabolites

  • Investigate potential YedZ substrates in planta

P. carotovorum is known to cause significant economic losses through soft rot diseases in diverse plants . The pathogen produces numerous plant cell wall-degrading enzymes , and redox proteins like YedZ may contribute to bacterial survival during infection by mediating adaptation to oxidative stress or by modifying host defense compounds.

How can cryo-electron microscopy be applied to determine the structure of membrane-embedded YedZ and its complexes?

Cryo-electron microscopy (cryo-EM) offers powerful approaches for structural analysis of YedZ as a membrane protein:

• Sample Preparation Optimization:

  • Use nanodiscs or amphipols to stabilize membrane proteins

  • Employ lipid composition matching the native bacterial membrane

  • Screen detergent types and concentrations for optimal protein stability

• Single Particle Analysis Protocol:

  • Vitrify samples on holey carbon grids

  • Collect data on high-end microscopes (e.g., Titan Krios with K3 detector)

  • Process data using software packages like RELION or cryoSPARC

  • Target resolution of 3.0-3.5 Å for membrane proteins

• Subtomogram Averaging for In-situ Studies:

  • Prepare bacterial membrane vesicles containing YedZ complexes

  • Collect tilt series and reconstruct tomograms

  • Extract and align membrane-embedded YedZ complexes

  • Resolve contextual information about native arrangement

• Validation Strategies:

  • Combine with crosslinking mass spectrometry (XL-MS)

  • Verify key interactions through mutagenesis

  • Use molecular dynamics simulations to assess model stability

• Challenge-Specific Considerations:

  • Address preferred orientation issues with tilted data collection

  • Use phase plates for improved contrast of small membrane proteins

  • Consider GraFix method to stabilize transient complexes

This comprehensive cryo-EM approach enables visualization of YedZ's membrane topology, heme coordination environment, and interactions with partner proteins in near-native conditions.

What computational approaches can predict YedZ substrates and potential inhibitors for antimicrobial development?

Advanced computational methods offer valuable tools for predicting YedZ substrates and identifying potential inhibitors:

• Homology Modeling and Molecular Dynamics:

  • Generate 3D models based on structurally characterized homologs

  • Refine models with explicit membrane/solvent molecular dynamics

  • Identify binding pockets and catalytic residues

• Virtual Screening Workflow:

  • Prepare libraries of potential substrates or inhibitors

  • Perform molecular docking against identified binding sites

  • Score and rank compounds based on predicted binding energy

  • Filter compounds by drug-likeness and synthetic accessibility

• Quantum Mechanics/Molecular Mechanics (QM/MM):

  • Model electron transfer reactions at the heme center

  • Calculate reaction barriers for candidate substrates

  • Predict effects of point mutations on catalytic efficiency

• Machine Learning Applications:

  • Train models on known sulfoxide reductase substrates

  • Develop classifiers for substrate prediction

  • Implement neural networks for activity prediction

• Comparative Analysis Framework:

These computational approaches provide testable hypotheses about YedZ function and guide experimental design for inhibitor development against P. carotovorum, potentially leading to new strategies for controlling plant diseases caused by this pathogen .

How can systems biology approaches integrate YedZ function into global models of P. carotovorum metabolism during plant infection?

Systems biology offers powerful frameworks to contextualize YedZ function within global bacterial metabolism during plant infection:

• Multi-omics Integration Strategy:

  • Combine transcriptomics, proteomics, and metabolomics data

  • Compare wild-type and ΔyedZ strains under infection conditions

  • Apply statistical methods (e.g., WGCNA, DIABLO) to identify co-regulated networks

  • Map changes to metabolic pathways using KEGG or BioCyc databases

• Flux Balance Analysis (FBA):

  • Construct genome-scale metabolic models for P. carotovorum

  • Include YedZ-dependent reactions based on experimental data

  • Simulate metabolic flux distributions under infection conditions

  • Identify critical pathways affected by YedZ function

• Regulatory Network Reconstruction:

  • Identify transcription factors affected by YedZ activity

  • Map regulatory interactions using ChIP-seq or DAP-seq

  • Construct dynamic models of gene regulation during infection

• Host-Pathogen Interaction Modeling:

  • Develop dual-organism metabolic models (plant and bacterium)

  • Simulate nutrient exchange and competition

  • Model redox balance at the host-pathogen interface

• Experimental Validation Cycle:

  • Design targeted experiments to test model predictions

  • Refine models with new experimental data

  • Iterate between computational prediction and experimental validation

Since P. carotovorum is known to produce numerous plant cell wall-degrading enzymes causing soft rot diseases , integrating YedZ function into these pathogenicity mechanisms can reveal how electron transport and sulfoxide metabolism contribute to bacterial survival and virulence during plant infection. This systems approach can identify potential intervention points for disease control strategies beyond conventional targets.

How can researchers optimize experimental conditions for studying YedZ-catalyzed reactions in vitro?

Optimizing in vitro experimental conditions for YedZ-catalyzed reactions requires systematic parameter adjustment:

• Buffer Optimization:

  • Test pH range (6.0-8.5) in 0.5 unit increments

  • Screen buffer systems (HEPES, Tris, phosphate) for compatibility

  • Optimize ionic strength (50-300 mM NaCl or KCl)

  • Evaluate effects of divalent cations (Mg²⁺, Ca²⁺) at 1-5 mM

• Redox Environment Control:

  • Maintain reducing conditions with DTT or β-mercaptoethanol (1-5 mM)

  • Test alternative reductants (TCEP, glutathione) if sulfur-containing reductants interfere

  • Consider anaerobic conditions using oxygen-scavenging systems for oxygen-sensitive assays

• Detergent Selection:

  • Maintain detergent above critical micelle concentration

  • Test detergent effects on activity (typically 0.01-0.05% for DDM)

  • Consider reconstitution into liposomes or nanodiscs for native-like environment

• Substrate Delivery Optimization:

  • For hydrophobic substrates, optimize solubilization methods

  • Test co-solvents (DMSO, ethanol) at concentrations that don't inhibit activity

  • Consider substrate delivery via liposomes for membrane-associated substrates

• Electron Transfer System:

  • Test physiological electron donors (NADH, NADPH)

  • Optimize mediator concentrations (methylene blue, phenazine methosulfate)

  • Establish suitable controls for non-enzymatic reactions

• Assay Development Matrix:

Systematic optimization using this framework enables reproducible and physiologically relevant measurements of YedZ catalytic activity.

How can CRISPR-Cas9 genome editing be applied to study YedZ function in P. carotovorum?

CRISPR-Cas9 genome editing offers powerful approaches for studying YedZ function in P. carotovorum:

• CRISPR System Adaptation for P. carotovorum:

  • Select appropriate Cas9 expression vectors for Gram-negative bacteria

  • Optimize codon usage for P. carotovorum

  • Use inducible promoters (tetR, araBAD) to control Cas9 expression

  • Design temperature-sensitive plasmid backbones for easy curing

• sgRNA Design Strategy:

  • Target unique sequences within yedZ gene

  • Select sites with minimal off-target potential using algorithms like CCTop

  • Design multiple sgRNAs targeting different regions of the gene

  • Include PAM sequences appropriate for the Cas9 variant used

• Editing Approaches:

  • Gene Knockout: Include homology arms (~500 bp) flanking yedZ

  • Point Mutations: Design repair templates with desired mutations

  • Tagged Versions: Create C-terminal fusions with reporters or affinity tags

  • Regulatable Expression: Replace native promoter with inducible systems

• Screening and Validation Protocol:

  • Design PCR primers spanning the edited region

  • Implement colony PCR screening strategy

  • Confirm edits by Sanger sequencing

  • Verify protein expression changes by Western blot

  • Assess phenotypic changes in growth and virulence

• Multiplexed Analysis:

  • Create combinatorial knockouts of yedZ with related genes

  • Generate libraries of point mutations to map functional domains

  • Apply CRISPRi for graded repression of yedZ expression

This comprehensive CRISPR-Cas9 strategy enables precise genetic manipulation of YedZ in P. carotovorum, facilitating detailed functional characterization and potentially revealing its role in bacterial pathogenicity, which is significant given that P. carotovorum causes significant economic losses through soft rot diseases in diverse plants .