Recombinant Photobacterium profundum UPF0060 membrane protein PBPRB0495 (PBPRB0495)

What is Recombinant Photobacterium profundum UPF0060 membrane protein PBPRB0495?

Recombinant Photobacterium profundum UPF0060 membrane protein PBPRB0495 is a full-length (1-110 amino acids) protein derived from the deep-sea bacterium Photobacterium profundum. The protein is typically expressed in E. coli expression systems with an N-terminal His-tag for purification purposes. The protein belongs to the UPF0060 membrane protein family, with the following amino acid sequence: MPELKTVGLFFITAIAEIIGCYLPYLWLREGKTIWLLIPAAISLALFAWLLTLHPAAAGRVYAAYGGVYIFTAILWLWLVDGIRPTVWDFVGVFVALLGMAIIMFSPRPA . As a membrane protein from a piezophilic (pressure-loving) organism, PBPRB0495 is of particular interest in studying pressure adaptation mechanisms in marine environments.

How should Recombinant PBPRB0495 protein be stored and reconstituted for experimental use?

For optimal stability, Recombinant PBPRB0495 protein should be stored at -20°C/-80°C upon receipt, with aliquoting necessary for multiple uses to avoid repeated freeze-thaw cycles. The lyophilized powder is typically stored in Tris/PBS-based buffer with 6% Trehalose at pH 8.0 . For reconstitution, first centrifuge the vial briefly to bring contents to the bottom, then reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL. For long-term storage, it is recommended to add glycerol to a final concentration of 5-50% (with 50% being standard) before aliquoting and storing at -20°C/-80°C . Working aliquots may be stored at 4°C for up to one week, but repeated freezing and thawing should be avoided as it can compromise protein integrity and experimental reproducibility.

What are the basic culturing conditions for Photobacterium profundum when studying pressure-related proteins?

Photobacterium profundum SS9 is typically cultured anaerobically at 17°C in marine broth (28 g/liter 2216 medium) supplemented with 20 mM glucose and 100 mM HEPES buffer (pH 7.5) . For stock cultures, -80°C freezer stock is inoculated into 15 ml of marine broth at 17°C in sterile plastic tubes and grown to an OD of 1.5 at 600 nm. For pressure experiments, cultures are aliquoted into sterile Pasteur pipettes (6 ml each), excluding air to ensure anaerobic conditions and even hydrostatic pressure distribution. The pipettes are then sealed and incubated at either atmospheric pressure (0.1 MPa) or high pressure (typically 28 MPa) at 17°C for 5 days . Growth is monitored by measuring optical density at 600 nm, while harvesting is performed by centrifugation at 800×g for 10 minutes, followed by snap-freezing and storage at -80°C for further analysis.

What role does accessibility of translation initiation sites play in recombinant protein expression success?

The accessibility of translation initiation sites, modeled using mRNA base-unpairing across Boltzmann's ensemble, is a critical factor in recombinant protein expression success. Research shows that this factor significantly outperforms alternative features in predicting expression outcomes. Analysis of 11,430 recombinant proteins from 189 diverse species expressed in E. coli demonstrated that accessibility captures key propensity beyond the target region, with even a modest number of synonymous changes being sufficient to tune recombinant protein expression levels . Higher accessibility correlates with higher protein production, though it may lead to slower cell growth due to resource allocation constraints. This understanding helps explain why approximately 50% of recombinant proteins fail to express adequately in host cells, despite having correct gene sequences. When designing expression constructs for PBPRB0495, optimizing the accessibility of translation initiation sites should be prioritized over simple codon optimization to improve expression yield.

How does hydrostatic pressure affect the expression and function of P. profundum membrane proteins like PBPRB0495?

Hydrostatic pressure creates a distinct ecological niche that fundamentally alters protein function and regulation in piezophilic organisms like P. profundum. Label-free quantitative proteomic analysis reveals that an important fraction of the P. profundum proteome is under tight regulation in response to pressure changes, with relatively abundant proteins being up- or down-regulated based on pressure conditions . Specifically, when comparing growth at atmospheric pressure (0.1 MPa) versus high pressure (28 MPa), drastically altered modes of protein function emerge. Membrane proteins like PBPRB0495 are particularly sensitive to pressure changes due to their location at the interface between the cell and its environment.

The physiological adaptation to pressure involves not just changes in protein abundance but also potential modifications in protein conformation, interaction partners, and localization within the membrane. Nutrient intake by P. profundum appears to be modulated by pressure, suggesting that membrane transport proteins may undergo functional adaptations . For membrane proteins like PBPRB0495, which likely play roles in maintaining membrane integrity or transport functions under pressure, experimental designs must account for these pressure-dependent changes. When studying PBPRB0495 specifically, researchers should compare its expression, localization, and interaction partners under various pressure conditions to elucidate its role in pressure adaptation mechanisms.

What experimental approaches are most effective for studying the structure-function relationship of PBPRB0495 under different pressure conditions?

For comprehensive investigation of PBPRB0495's structure-function relationship under varying pressure conditions, a multi-modal approach is recommended. First, high-pressure cultivation systems should be employed using sealed Pasteur pipettes containing marine broth with appropriate supplements, incubated in water-cooled pressure vessels capable of maintaining 0.1-40 MPa at controlled temperatures (17°C) . To study membrane localization and topology, membrane fractionation followed by proteomic analysis is crucial, as "a more focused study on how P. profundum perceives pressure changes would benefit from a membrane enrichment strategy" .

For structural studies, a combination of X-ray crystallography (at atmospheric pressure) and high-pressure NMR or SAXS (Small Angle X-ray Scattering) can provide insights into pressure-induced conformational changes. Functional characterization should include liposome reconstitution experiments to assess transport or signaling activities under pressure. For in vivo studies, fluorescence microscopy with pressure-resistant optical cells can track protein localization and dynamics in living cells.

Comparative analysis with homologous proteins from non-piezophilic organisms can highlight pressure-specific adaptations. Additionally, site-directed mutagenesis targeting key residues (particularly in transmembrane regions identified in the amino acid sequence: MPELKTVGLFFITAIAEIIGCYLPYLWLREGKTIWLLIPAAISLALFAWLLTLHPAAAGRVYAAYGGVYIFTAILWLWLVDGIRPTVWDFVGVFVALLGMAIIMFSPRPA) can reveal structure-function relationships critical for pressure adaptation . This integrated approach allows researchers to correlate structural features with functional properties across pressure gradients.

What factors influence the successful heterologous expression of Photobacterium profundum membrane proteins in E. coli systems?

Successful heterologous expression of P. profundum membrane proteins like PBPRB0495 in E. coli systems depends on multiple factors that must be optimized simultaneously. Translation initiation efficiency represents a critical determinant, with accessibility of translation initiation sites being particularly significant. Analysis of 11,430 recombinant proteins showed that mRNA base-unpairing across the Boltzmann's ensemble significantly outperforms alternative features in predicting expression success . For membrane proteins specifically, the accessibility model captures key propensity beyond the target region, whereby modest synonymous changes in the first nine codons can substantially improve expression.

Beyond sequence optimization, expression conditions must be carefully controlled. Growth temperature modulation (typically lowering to 17-20°C post-induction) helps prevent inclusion body formation by slowing protein synthesis and allowing proper folding and membrane insertion. Appropriate induction timing and inducer concentration are critical, with late-log phase induction and lower inducer concentrations often yielding better results for membrane proteins.

The choice of E. coli strain also impacts success, with C41(DE3) and C43(DE3) strains being preferred for membrane proteins due to their adaptations for toxic membrane protein expression. Incorporation of fusion partners (such as the N-terminal His-tag used in recombinant PBPRB0495) can enhance solubility and facilitate purification, though tag position must be optimized to prevent interference with membrane insertion.

For maximum yield, specialized membrane-protein-friendly media formulations with optimized phosphate concentrations and supplemented with glucose (20 mM) may improve expression outcomes. Post-extraction stabilization using appropriate detergents is essential for maintaining protein structure and function during purification and subsequent experiments.

How do you distinguish between pressure-specific adaptations and general stress responses when analyzing differential expression of PBPRB0495?

Distinguishing pressure-specific adaptations from general stress responses requires a carefully designed experimental approach with appropriate controls and comparative analyses. First, implement a factorial experimental design that varies both pressure (0.1 MPa vs. 28 MPa) and other stress factors independently (temperature, nutrient limitation, oxygen availability) . This allows statistical separation of pressure-specific effects from general stress responses.

Time-course experiments are crucial, as pressure-specific adaptations often follow different temporal patterns than general stress responses. General stress responses typically activate rapidly and transiently, while pressure adaptations may involve sustained expression changes. Comparing the expression profiles of PBPRB0495 with known general stress response proteins (like chaperones and proteases) can highlight divergent patterns.

Comparative genomics and phylogenetic analysis provide another valuable approach. Identifying PBPRB0495 homologs in non-piezophilic organisms and comparing their regulation under various stresses can highlight pressure-unique adaptations. Similarly, comparing PBPRB0495 expression with homologous proteins in other piezophilic bacteria can reveal conserved pressure-response mechanisms.

For definitive functional evidence, genetic manipulation experiments are essential. Constructing PBPRB0495 knockout or overexpression strains and testing their growth and survival under different pressure conditions versus other stressors can demonstrate pressure-specific functions. Complementation studies, where the wild-type gene is reintroduced to knockout strains, can confirm phenotype specificity.

A quantitative proteomics approach comparing protein abundance changes under pressure versus other stressors provides comprehensive data for statistical discrimination between stress types. The data can be analyzed using principal component analysis or other multivariate statistical methods to separate pressure-specific from general stress response protein clusters.

What is the recommended protocol for purification of recombinant PBPRB0495 protein while maintaining its structural integrity?

The purification of recombinant PBPRB0495 requires specialized techniques to maintain the structural integrity of this membrane protein. Below is a detailed methodological approach:

Initial Preparation:

• Express the His-tagged recombinant protein in E. coli under optimized conditions (17°C, late-log phase induction)

• Harvest cells by centrifugation at 5,000×g for 15 minutes at 4°C

• Resuspend cell pellet in lysis buffer (50 mM Tris-HCl pH 8.0, 150 mM NaCl, 1 mM PMSF, 1 mg/mL lysozyme)

Membrane Extraction:

• Disrupt cells by sonication or French press (10 cycles, 30s on/30s off)

• Remove cell debris by centrifugation at 10,000×g for 20 minutes at 4°C

• Ultracentrifuge the supernatant at 100,000×g for 1 hour at 4°C to isolate membrane fraction

• Resuspend membrane pellet in solubilization buffer (50 mM Tris-HCl pH 8.0, 150 mM NaCl, 1% n-dodecyl β-D-maltoside or other appropriate detergent)

• Incubate with gentle rotation at 4°C for 2 hours to solubilize membrane proteins

Affinity Purification:

• Equilibrate Ni-NTA resin with binding buffer (50 mM Tris-HCl pH 8.0, 150 mM NaCl, 0.1% selected detergent, 10 mM imidazole)

• Apply solubilized membrane fraction to resin and incubate with gentle rotation for 1 hour at 4°C

• Wash with increasing concentrations of imidazole (20 mM, 40 mM) to remove non-specific binding

• Elute PBPRB0495 protein with elution buffer (50 mM Tris-HCl pH 8.0, 150 mM NaCl, 0.1% detergent, 250 mM imidazole)

Size Exclusion Chromatography:

• Further purify the eluted protein using size exclusion chromatography

• Concentrate sample using 10 kDa MWCO concentrator to 2-5 mL

• Load onto Superdex 200 column equilibrated with final buffer (50 mM Tris-HCl pH 8.0, 150 mM NaCl, 0.05% detergent)

• Collect fractions and analyze by SDS-PAGE for purity (should be greater than 90%)

Storage and Stabilization:

• Pool pure fractions and concentrate to desired concentration

• Add glycerol to 6-50% final concentration

• Aliquot and flash-freeze in liquid nitrogen

• Store at -80°C for long-term storage or at 4°C for up to one week for immediate use

Quality Control:

• Verify protein identity by mass spectrometry

• Assess secondary structure integrity by circular dichroism

• Evaluate oligomeric state by blue native PAGE or analytical ultracentrifugation

This protocol is specifically designed to maintain the native-like structure of PBPRB0495 throughout the purification process, which is essential for subsequent structural and functional studies.

What experimental design is optimal for comparing PBPRB0495 expression and function under different pressure conditions?

An optimal experimental design for comparing PBPRB0495 expression and function under different pressure conditions requires careful control of variables and appropriate analytical methods. The following methodological approach is recommended:

Culture Setup:

• Prepare P. profundum SS9 cultures anaerobically at 17°C in marine broth supplemented with 20 mM glucose and 100 mM HEPES buffer (pH 7.5)

• Use a minimum of biological triplicates for statistical validity

• Aliquot cultures into sealed, air-free Pasteur pipettes (6 mL each) for even pressure distribution

• Establish at least three pressure conditions: atmospheric (0.1 MPa), moderate (10 MPa), and high pressure (28 MPa)

• Include a time-course component with sampling at early logarithmic, mid-logarithmic, and stationary phases

Data Collection Matrix:

Analytical Methods:

• Growth Monitoring: Measure optical density at 600 nm for growth curves

• Transcriptional Analysis:

  • Extract total RNA using RNeasy kits with DNase treatment

  • Perform qRT-PCR targeting PBPRB0495 gene with appropriate reference genes

  • Analyze using the 2^-ΔΔCt method with statistical evaluation

• Protein Expression:

  • Prepare membrane fractions through differential centrifugation

  • Perform Western blot analysis using anti-His antibodies for recombinant PBPRB0495

  • Quantify relative and absolute protein abundance by label-free MS methods

• Functional Characterization:

  • Assess membrane integrity through fluorescent dye exclusion assays

  • Measure transport activity (if applicable) using radioactive or fluorescent substrates

  • Determine protein-protein interactions through co-immunoprecipitation

  • Analyze membrane fluidity using fluorescence anisotropy

Data Analysis:

• Apply two-way ANOVA to determine significant effects of pressure, growth phase, and their interaction

• Use principal component analysis to identify patterns in multivariate data

• Perform correlation analysis between transcriptomic, proteomic, and functional data

• Create comprehensive heatmaps to visualize expression patterns across conditions

This experimental design allows for robust statistical analysis of pressure effects on PBPRB0495 expression and function while controlling for growth phase variation and providing multiple levels of evidence through complementary analytical techniques.

How can researchers optimize mRNA accessibility for improved expression of PBPRB0495 in heterologous systems?

Optimizing mRNA accessibility for improved expression of PBPRB0495 in heterologous systems requires a systematic approach focused on the translation initiation region. The following methodological strategy is recommended:

Computational Analysis and Design:

• Calculate the accessibility (base-unpairing probabilities) of the translation initiation site using algorithms that model the Boltzmann ensemble of RNA structures

• Use tools like TIsigner that employ simulated annealing to modify the first nine codons with synonymous substitutions while maintaining the amino acid sequence

• Generate multiple sequence variants with progressively higher accessibility scores

• Compare these designs with traditional codon optimization approaches that focus only on codon adaptation index (CAI)

Experimental Validation Protocol:

• Synthesize a minimum of 5-6 gene variants with varying accessibility scores

• Clone these variants into expression vectors maintaining identical promoters, ribosome binding sites, and tags

• Transform into appropriate E. coli strains (e.g., C41(DE3) for membrane proteins)

• Implement a factorial design testing:

  • Different growth temperatures (17°C, 25°C, 30°C)

  • Various inducer concentrations (0.1 mM, 0.5 mM, 1.0 mM IPTG)

  • Multiple induction times (early, mid, late log phase)

Accessibility Optimization Matrix:

Expression Analysis:

• Quantify protein expression through:

  • Western blotting with anti-His antibodies (for relative comparison)

  • Purification and yield determination (for absolute quantification)

  • Cell growth monitoring to assess protein production cost

• Analyze membrane integration efficiency using membrane fractionation

• Assess protein functionality through appropriate activity assays

Advanced Refinement:

• For the best-performing variants, implement a second round of optimization focusing on:

  • Fine-tuning the 5' UTR structure

  • Optimizing the spacing between the Shine-Dalgarno sequence and start codon

  • Eliminating any remaining internal Shine-Dalgarno-like sequences that might cause ribosome pausing

• Consider co-expression with appropriate chaperones specific for membrane proteins

• Test expression in specialized strains engineered for improved membrane protein production

Validation Criteria:
The optimized construct should demonstrate:

• At least 2-fold improvement in expression compared to wild-type sequence

• Proper membrane localization confirmed by fractionation

• Functional activity comparable to the native protein

• Reproducible expression across multiple induction conditions

This systematic approach based on accessibility optimization rather than simple codon optimization has been shown to significantly improve recombinant protein expression, particularly for challenging proteins like membrane proteins from diverse species .

What analytical techniques are most informative for studying pressure-dependent conformational changes in PBPRB0495?

A comprehensive analysis of pressure-dependent conformational changes in PBPRB0495 requires multiple complementary analytical techniques. The following methodological approach combines both in vitro and in silico methods:

High-Pressure Biophysical Techniques:

• High-Pressure NMR Spectroscopy

  • Prepare 15N or 13C/15N-labeled PBPRB0495 in detergent micelles or nanodiscs

  • Acquire 1H-15N HSQC spectra at pressures ranging from 0.1 to 100 MPa

  • Monitor chemical shift perturbations to identify pressure-sensitive residues

  • Determine pressure-dependent changes in dynamics through relaxation measurements

• High-Pressure Circular Dichroism (HP-CD)

  • Monitor secondary structure changes as a function of pressure

  • Collect spectra at 5 MPa increments from 0.1 to 50 MPa

  • Analyze using deconvolution algorithms to quantify α-helix, β-sheet, and random coil content

  • Create pressure-dependent secondary structure profiles

• High-Pressure FTIR Spectroscopy

  • Focus on amide I band (1600-1700 cm-1) to detect secondary structure changes

  • Implement difference spectroscopy between pressure points

  • Calculate pressure-induced frequency shifts of characteristic bands

• Fluorescence Spectroscopy under Pressure

  • Introduce environment-sensitive fluorescent probes at strategic positions

  • Monitor tryptophan fluorescence for tertiary structure changes

  • Implement FRET pairs to measure distance changes between domains

  • Analyze fluorescence lifetime and anisotropy under varying pressure

Complementary Structural Methods:

• Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS)

  • Compare exchange rates at different pressures to identify regions with altered solvent accessibility

  • Perform time-course experiments (30s, 1min, 5min, 30min exchange times)

  • Analyze peptide fragments to map pressure-sensitive regions

• Molecular Dynamics Simulations

  • Create membrane-embedded models of PBPRB0495 based on its amino acid sequence

  • Perform simulations at different pressures (0.1, 10, 28, 50 MPa)

  • Analyze root-mean-square fluctuations, hydrogen bonding networks, and cavity volumes

  • Identify pressure-sensing motifs and conformational transitions

Data Integration Protocol:

• Multi-dimensional Data Analysis

  • Correlate results from different techniques using statistical methods

  • Implement principal component analysis to identify major conformational states

  • Create pressure-response maps highlighting sensitive regions

• Structure-Function Correlation

  • Design activity assays that can be performed under pressure

  • Correlate conformational changes with functional parameters

  • Develop mathematical models relating pressure, structure, and function

Analytical Data Presentation Template:

This multi-technique approach provides a comprehensive view of pressure-dependent conformational changes in PBPRB0495, allowing researchers to identify critical pressure-sensing domains and potential mechanisms for pressure adaptation in this membrane protein.

What potential biotechnological applications exist for pressure-adapted membrane proteins like PBPRB0495?

Pressure-adapted membrane proteins like PBPRB0495 from Photobacterium profundum offer unique structural and functional properties that can be harnessed for various biotechnological applications. These proteins have evolved to function optimally under high hydrostatic pressure conditions, making them valuable for processes requiring pressure stability or pressure-modulated activity.

One promising application is in biocatalysis under extreme conditions. Pressure-adapted membrane proteins can be utilized as catalysts in high-pressure bioprocessing, where conventional enzymes might denature or lose function. PBPRB0495, with its transmembrane structure and potential transport or signaling capabilities, could be engineered to serve as a pressure-stable scaffold for creating novel biocatalysts that operate efficiently under industrial high-pressure conditions.

For pharmaceutical applications, pressure-adapted membrane proteins offer templates for designing pressure-resistant drug delivery systems. By understanding the molecular mechanisms that allow PBPRB0495 to maintain structural integrity under pressure, researchers can design liposomal or nanoparticle-based drug carriers that remain stable during high-pressure homogenization processes used in pharmaceutical manufacturing .

In synthetic biology, PBPRB0495 could serve as a building block for creating pressure-responsive cellular circuits. By integrating pressure-sensing domains identified from PBPRB0495 into synthetic signaling pathways, researchers could develop microbial systems that respond to pressure changes in controlled and predictable ways, enabling new applications in environmental monitoring or industrial bioprocessing.

The food industry could benefit from pressure-adapted proteins in the development of high-pressure processing technologies. PBPRB0495's stability under pressure could inform the design of processing aids or protective additives that maintain food quality during high-pressure pasteurization or sterilization processes.

For environmental biotechnology, pressure-adapted proteins could enhance bioremediation in deep-sea environments affected by pollution. Engineered microorganisms containing pressure-optimized membrane transport systems based on PBPRB0495 could efficiently remove contaminants from deep-sea oil spills or mining sites.

The detailed research on PBPRB0495 also contributes to understanding fundamental principles of protein pressure adaptation, potentially leading to general rules for engineering pressure-stable proteins for various industrial applications requiring extreme conditions.

How might comparative analysis of PBPRB0495 with homologous proteins from non-piezophilic organisms advance our understanding of pressure adaptation mechanisms?

Comparative analysis of PBPRB0495 with homologous proteins from non-piezophilic organisms provides a powerful approach to uncover the molecular basis of pressure adaptation. By contrasting sequence, structure, and functional characteristics, researchers can identify specific adaptations that enable survival and function under high hydrostatic pressure.

At the sequence level, alignment of PBPRB0495 with homologs from non-piezophilic bacteria may reveal consistent substitution patterns associated with pressure adaptation. Previous studies on pressure-adapted proteins have identified trends toward increased flexibility in certain regions while maintaining rigid structural cores. For PBPRB0495, with its amino acid sequence MPELKTVGLFFITAIAEIIGCYLPYLWLREGKTIWLLIPAAISLALFAWLLTLHPAAAGRVYAAYGGVYIFTAILWLWLVDGIRPTVWDFVGVFVALLGMAIIMFSPRPA , comparative analysis might reveal pressure-specific substitutions in transmembrane domains or connecting loops.

Structural comparison using homology modeling or experimental structures can identify differences in packing density, cavity volumes, and flexibility. Pressure-adapted proteins often feature reduced internal cavities and altered hydrophobic cores that resist pressure-induced water infiltration. For membrane proteins like PBPRB0495, comparative analysis might reveal adaptations in lipid-protein interfaces that maintain function despite pressure-induced membrane compression.

Functional comparison through heterologous expression experiments provides direct evidence of pressure adaptation. By expressing PBPRB0495 and its non-piezophilic homologs in the same host system and testing function across pressure gradients, researchers can quantify the pressure adaptation magnitude. Such experiments might involve measuring transport activity, membrane integrity, or protein-protein interactions under varying pressure conditions.

The comparative analysis can be extended to investigate evolutionary aspects of pressure adaptation. Phylogenetic analysis can determine whether pressure adaptations in PBPRB0495 arose from convergent evolution or represent ancestral traits. This information helps establish general principles of pressure adaptation applicable to protein engineering.

From a practical perspective, a database of pressure-adapted features identified through comparative analysis could guide rational design of pressure-resistant proteins for biotechnological applications. The comparison of PBPRB0495 with non-piezophilic homologs not only advances basic understanding of pressure biology but also enables development of predictive models for pressure effects on protein structure and function.