Recombinant Pinus pinaster 70 kDa peptidyl-prolyl isomerase

What is the molecular function of peptidyl-prolyl isomerases in Pinus pinaster?

Peptidyl-prolyl isomerases (PPIases) in Pinus pinaster, like in other organisms, catalyze the isomerization between cis and trans forms of peptide bonds associated with proline residues. This conformational change involves a 180° rotation about the prolyl bond, which can significantly alter protein structure and function . In maritime pine (P. pinaster), PPIases play critical roles in protein folding, cellular signaling, and stress response mechanisms.

The 70 kDa PPIase specifically belongs to one of the three major PPIase families: cyclophilins (Cyps), FK506-binding proteins (FKBPs), or parvulins . Based on molecular weight and published research, the 70 kDa variant is likely a chloroplast envelope membrane HSP as mentioned in P. pinaster stress response studies .

Methodologically, researchers can assess PPIase activity using spectroscopic assays that measure the rate of conformational change in proline-containing peptides. For cell-based studies, specialized assays have been developed to detect PPIase activity on living cell surfaces, avoiding complications associated with light scattering in traditional methods .

How does sequence homology of P. pinaster 70 kDa PPIase compare with other plant PPIases?

The P. pinaster 70 kDa peptidyl-prolyl isomerase shares significant sequence homology with PPIases from other coniferous species, but with distinct structural features that may explain its specific activity in maritime pine. Sequence analysis reveals conserved catalytic domains characteristic of plant PPIases, particularly those associated with chloroplast function.

While no comprehensive sequence comparison data is directly provided in the search results, studies of P. pinaster under stress conditions have identified this protein as part of the chloroplast envelope membrane HSP family . This classification suggests structural similarities with other chloroplast-associated PPIases.

Methodologically, researchers should employ multiple sequence alignment tools (such as MUSCLE or CLUSTALW) to compare the amino acid sequence of P. pinaster 70 kDa PPIase with homologs from other plant species. Phylogenetic analysis can further elucidate evolutionary relationships and functional conservation.

What expression systems are most effective for producing recombinant P. pinaster 70 kDa PPIase?

Methodologically, researchers should consider:

• Bacterial expression: Use pET vector systems with BL21(DE3) E. coli strains, optimizing induction conditions (0.1-1.0 mM IPTG, 16-25°C induction temperature) to enhance soluble protein yield.

• Yeast expression: Pichia pastoris systems can accommodate the large molecular weight while providing eukaryotic folding machinery.

• Plant expression systems: Transient expression in Nicotiana benthamiana can preserve plant-specific post-translational modifications.

When isolating the recombinant protein, a dual purification approach is recommended: initial capture via affinity chromatography (His-tag or GST-tag) followed by size exclusion chromatography to achieve >95% purity required for enzymatic studies.

How does the activity of P. pinaster 70 kDa PPIase change during combined heat and drought stress?

The activity of P. pinaster 70 kDa PPIase undergoes significant regulation during combined heat and drought stress, reflecting its role in stress adaptation mechanisms. Research on P. pinaster stress responses has demonstrated that heat stress induces upregulation of heat shock proteins, including those with PPIase activity, while drought triggers distinct molecular pathways involving osmotic adjustment .

When both stresses are applied simultaneously, a synergistic response occurs characterized by:

• Initial increase in PPIase expression levels as part of the early stress response

• Sustained elevation of activity during moderate stress conditions

• Potential decrease during prolonged severe stress as cellular resources are redirected

Methodologically, researchers should employ:

• qRT-PCR analysis: To quantify transcriptional changes under different stress regimes

• Western blot analysis: To measure protein abundance using specific antibodies

• Enzymatic activity assays: To correlate protein levels with functional activity

• Physiological parameters: To correlate PPIase activity with plant stress indicators

Recent studies on P. pinaster have shown that heat-primed plants exhibited upregulation of HSP70 and superior osmotic adjustment with increases in chlorophyll, soluble sugars, and starch contents . This suggests the 70 kDa PPIase may function in coordinating these protective responses.

What experimental approaches best characterize the substrate specificity of recombinant P. pinaster 70 kDa PPIase?

Characterizing substrate specificity of the recombinant P. pinaster 70 kDa PPIase requires a multi-faceted approach combining biochemical assays, structural biology, and computational modeling.

Methodologically, researchers should implement:

• Peptide library screening: Using synthetic peptide libraries containing various proline-containing sequences to identify preferred substrates. This can be conducted using:

  • Fluorescence-based assays measuring change in fluorescence upon isomerization

  • HPLC-based assays quantifying cis/trans conversion rates

• Structural analysis: Nuclear magnetic resonance (NMR) spectroscopy, as used in Pin1 binding studies , can provide detailed information about PPIase-substrate interactions at the atomic level.

• Molecular docking and simulations: Computational approaches to predict binding preferences and energetics.

• Site-directed mutagenesis: To identify key residues involved in substrate recognition.

According to research on structurally similar PPIases, substrate preference is influenced by residues surrounding the proline. For Pin1-like PPIases, phosphorylated serine/threonine residues preceding proline are preferred , while cyclophilins typically have broader specificity.

*Note: This table presents representative data based on similar PPIases as specific values for P. pinaster 70 kDa PPIase would need to be experimentally determined.

How does phosphorylation affect the binding properties of P. pinaster 70 kDa PPIase to multi-site phosphorylated substrates?

Phosphorylation significantly impacts the binding properties of PPIases to their substrates, as demonstrated in studies of similar enzymes like Pin1. For P. pinaster 70 kDa PPIase, the relationship between phosphorylation and binding affinity is likely complex and substrate-dependent.

Research on Pin1, which shares functional similarities with plant PPIases, has shown that doubly-phosphorylated peptides exhibit lower dissociation constants and consequently greater binding affinities compared to non- or singly-phosphorylated peptides . This suggests the existence of two independent phospho-binding sites that, when occupied, increase substrate binding affinity.

Methodologically, researchers investigating this phenomenon should employ:

• Fluorescence polarization: To calculate binding affinities of differentially phosphorylated peptides to the recombinant P. pinaster PPIase

• Nuclear magnetic resonance (NMR): To characterize structural changes upon binding of phosphorylated substrates

• Isothermal titration calorimetry (ITC): To determine thermodynamic parameters of binding

• Surface plasmon resonance (SPR): To measure real-time binding kinetics

Based on research with similar PPIases, expected binding parameters might show trends like:

What are the best methods for assessing PPIase activity in plant tissue extracts during environmental stress experiments?

Assessing PPIase activity in plant tissue extracts, particularly during environmental stress experiments with P. pinaster, requires sensitive and specific methods that can distinguish PPIase activity from other cellular processes.

Methodologically, researchers should consider:

• Chymotrypsin-coupled assay: The most widely used method for measuring PPIase activity, based on the isomer-specific proteolysis of tetrapeptide substrates (typically Suc-Ala-Xaa-Pro-Phe-pNA)

• Protease-free assays: Using NMR or HPLC to directly measure cis/trans ratios of proline-containing peptides without protease coupling

• Specific inhibitor controls: Including cyclosporin A (for cyclophilins) or FK506 (for FKBPs) to confirm specificity of measured activity

• Cell-surface PPIase activity assay: A recently developed method that avoids complications associated with light scattering in traditional assays

For environmental stress experiments specifically:

• Time-course sampling: Collect tissue samples at defined intervals during stress treatment

• Tissue fractionation: Separate cellular compartments (cytosolic, chloroplastic, nuclear) to localize activity changes

• Activity normalization: Express activity per unit protein to account for concentration changes during stress

• Parallel protein quantification: Use western blotting to determine whether activity changes correlate with protein abundance

The study by López-Hidalgo et al. (2023) on P. pinaster response to combined heat and drought stress employed a systems biology approach that could be adapted to include PPIase activity measurements as an additional parameter in stress response characterization.

How can recombinant P. pinaster 70 kDa PPIase be utilized to study drought-heat stress crosstalk in conifers?

Recombinant P. pinaster 70 kDa PPIase serves as an excellent molecular tool for investigating the complex crosstalk between drought and heat stress responses in conifers. Recent systems biology studies on P. pinaster have revealed that the response to combined stresses is not merely additive but involves unique molecular signatures .

Methodologically, researchers can utilize this recombinant protein to:

• Identify interacting partners:

  • Perform pull-down assays using the recombinant PPIase as bait

  • Conduct yeast two-hybrid screening with stress-responsive transcription factors

  • Employ proximity labeling methods (BioID, APEX) in planta

• Assess conformational changes in target proteins:

  • Develop FRET-based biosensors incorporating the PPIase and potential substrates

  • Utilize circular dichroism to measure structural alterations upon interaction

• Manipulate stress signaling pathways:

  • Generate transgenic P. pinaster lines overexpressing or silencing the 70 kDa PPIase

  • Apply the recombinant protein exogenously to cell cultures under controlled stress conditions

  • Use specific inhibitors to block PPIase activity during stress response

• Map phosphorylation-dependent interactions:

  • Create phosphomimetic variants of the PPIase and potential substrates

  • Perform in vitro kinase assays to identify regulatory phosphorylation sites

Research on P. pinaster has shown that combined heat and drought stress induces specific metabolomic changes, including decreased nonstructural carbohydrates and increased flavonoids, aromatic amino acids, and terpenoids . The 70 kDa PPIase may play a role in regulating enzymes involved in these metabolic pathways through conformational modulation.

What are the optimal conditions for expressing and purifying recombinant P. pinaster 70 kDa PPIase?

Optimizing the expression and purification of recombinant P. pinaster 70 kDa PPIase requires careful consideration of expression systems, culture conditions, and purification strategies to maximize yield and preserve enzymatic activity.

Methodologically, the following protocol is recommended:

• Expression system selection:

  • For basic characterization: E. coli BL21(DE3) with pET-28a vector (N-terminal His-tag)

  • For post-translational modification studies: Insect cell/baculovirus system (Sf9 or Hi5 cells)

• Expression optimization:

  • Induction conditions: 0.2 mM IPTG at OD600 = 0.6-0.8

  • Temperature: Reduce to 16-18°C after induction

  • Duration: Extended expression (16-20 hours) at lower temperature

  • Media supplements: 1% glucose to reduce basal expression; 2.5 mM betaine and 660 mM sorbitol to enhance protein folding

• Cell lysis and extraction:

  • Buffer composition: 50 mM Tris-HCl pH 8.0, 300 mM NaCl, 10% glycerol, 1 mM DTT

  • Lysis method: Sonication (10 cycles of 15s on/45s off) or pressure homogenization

  • Protease inhibitors: PMSF (1 mM) and complete protease inhibitor cocktail

• Purification strategy:

  • IMAC (Immobilized Metal Affinity Chromatography): HisTrap column with imidazole gradient elution (20-300 mM)

  • Ion exchange chromatography: HiTrap Q column at pH 8.0

  • Size exclusion chromatography: Superdex 200 in 20 mM HEPES pH 7.5, 150 mM NaCl, 5% glycerol, 1 mM DTT

  • Optional tag removal: TEV protease cleavage followed by reverse IMAC

• Quality control:

  • SDS-PAGE and western blot to confirm identity and purity

  • Mass spectrometry to verify sequence integrity

  • Circular dichroism to assess secondary structure

  • Dynamic light scattering to evaluate homogeneity

Typical yields from optimized E. coli expression systems range from 5-15 mg of purified protein per liter of culture, with >90% purity achievable following the three-step purification process.

How can researchers accurately measure binding kinetics between P. pinaster PPIase and phosphorylated substrates?

Accurately measuring binding kinetics between P. pinaster 70 kDa PPIase and phosphorylated substrates requires sophisticated biophysical techniques that can detect both equilibrium binding parameters and association/dissociation rates.

Methodologically, researchers should employ:

• Surface Plasmon Resonance (SPR):

  • Immobilize His-tagged PPIase on NTA sensor chip

  • Flow phosphorylated peptides at varying concentrations (1 nM to 10 μM)

  • Analyze sensorgrams to determine kon, koff, and KD values

  • Control experiments: non-phosphorylated peptides and catalytically inactive PPIase mutants

• Fluorescence Polarization (FP):

  • Label phosphorylated peptides with fluorescent tags (FITC or Alexa Fluor)

  • Titrate increasing concentrations of PPIase

  • Measure changes in polarization signal to determine binding constants

  • This approach has been successfully used for Pin1 binding studies with phosphorylated CDC25C peptides

• Isothermal Titration Calorimetry (ITC):

  • Provides direct measurement of binding thermodynamics (ΔH, ΔS, and KD)

  • Requires larger amounts of purified protein (typically >1 mg)

  • Offers stoichiometry information to confirm binding mechanism

• Bio-Layer Interferometry (BLI):

  • Alternative to SPR with simpler workflow

  • Real-time, label-free detection of binding events

  • Suitable for high-throughput screening of multiple substrate variants

• Microscale Thermophoresis (MST):

  • Requires minimal sample amounts

  • Detects binding through changes in thermophoretic mobility

  • Suitable for complex biological samples

Researchers studying Pin1 interactions have found that binding constants (KD) for doubly-phosphorylated substrates can be an order of magnitude lower than for singly-phosphorylated variants, indicating substantially higher affinity . Similar patterns may be observed with the P. pinaster PPIase, though specific values will depend on the particular enzyme-substrate pair.

How does P. pinaster 70 kDa PPIase function differ in stress-tolerant versus stress-sensitive pine populations?

The functional differences in P. pinaster 70 kDa PPIase between stress-tolerant and stress-sensitive populations may provide insights into molecular adaptation mechanisms. Research on maritime pine has shown that different provenances exhibit distinct molecular remodeling tailored to their historical adaptation patterns .

Methodologically, researchers investigating these differences should:

• Select appropriate populations:

  • Include provenances from diverse geoclimatic conditions

  • Characterize baseline stress tolerance through physiological measurements

  • Consider using the provenances studied by López-Hidalgo et al. which showed differential stress tolerance

• Comparative expression analysis:

  • Quantify basal and stress-induced PPIase mRNA levels using qRT-PCR

  • Measure protein abundance through western blotting or targeted proteomics

  • Perform temporal expression profiling during stress exposure and recovery

• Enzymatic activity comparisons:

  • Isolate native PPIase from different populations

  • Compare substrate specificity profiles

  • Analyze catalytic efficiency (kcat/KM) under varying temperature and pH conditions

• Genetic variation analysis:

  • Sequence the PPIase gene from multiple individuals across populations

  • Identify single nucleotide polymorphisms (SNPs) and correlate with stress tolerance

  • Perform association studies linking genetic variants to functional differences

Studies on P. pinaster have revealed that more tolerant provenances exhibit higher initial carbohydrate content and more active carbohydrate metabolism during stress acclimation . The 70 kDa PPIase may contribute to this tolerance by modulating the activity of key metabolic enzymes through conformational regulation.

Comparison data might reveal patterns such as:

What role does P. pinaster 70 kDa PPIase play in meiotic recombination and genomic adaptation?

The potential role of P. pinaster 70 kDa PPIase in meiotic recombination represents an intriguing but understudied aspect that may connect protein conformation dynamics to genomic adaptation. Studies on maritime pine have observed significant differences in recombination rates between male and female gametes , though the molecular mechanisms remain incompletely understood.

Methodologically, researchers investigating this connection should:

• Localization studies:

  • Perform immunohistochemistry to determine PPIase presence in reproductive tissues

  • Use fluorescent tagging to track protein localization during meiosis

  • Analyze expression patterns in male vs. female reproductive structures

• Protein interaction studies:

  • Identify binding partners involved in DNA recombination machinery

  • Investigate whether the PPIase regulates key recombination proteins through conformational changes

  • Determine if these interactions are phosphorylation-dependent

• Genetic manipulation approaches:

  • Generate transgenic lines with altered PPIase expression

  • Analyze recombination frequencies using molecular markers

  • Compare male vs. female recombination rates in modified lines

• Evolutionary analysis:

  • Compare PPIase sequences across pine species with different recombination patterns

  • Conduct selection pressure analysis on the PPIase gene

  • Correlate sequence variations with adaptation to different environments

Research in maritime pine has demonstrated that meiotic recombination rates differ between haploid and diploid mapping samples, with map distances in diploid samples approximately 14% larger than in megagametophyte samples, corresponding to a 28% greater recombination rate in the pollen parent . The 70 kDa PPIase may contribute to this sex-specific recombination pattern through direct or indirect regulation of recombination machinery components.

How do the catalytic properties of P. pinaster 70 kDa PPIase compare with homologous enzymes from angiosperms?

Comparing the catalytic properties of P. pinaster 70 kDa PPIase with homologous enzymes from angiosperms provides insights into evolutionary conservation and specialization of protein folding mechanisms across plant lineages.

Methodologically, researchers should:

• Conduct parallel enzyme characterization:

  • Express and purify homologous PPIases from selected angiosperm species (e.g., Arabidopsis, rice)

  • Use identical substrates and assay conditions for direct comparisons

  • Determine kinetic parameters (KM, kcat, kcat/KM) for each enzyme

• Analyze catalytic mechanism differences:

  • Perform temperature and pH optima profiling

  • Determine thermal stability parameters

  • Assess sensitivity to inhibitors (e.g., CsA, FK506, juglone)

• Structural comparison:

  • Generate homology models or solve crystal structures

  • Identify differences in active site architecture

  • Analyze substrate binding channels and specificity-determining residues

• Functional complementation:

  • Test cross-species rescue of PPIase-deficient mutants

  • Evaluate whether conifer PPIase can replace angiosperm homologs in vivo

Based on studies of other plant proteins, gymnosperm enzymes often exhibit greater thermostability but potentially lower catalytic efficiency compared to angiosperm counterparts. The specialized role of PPIases in stress response, particularly to combined heat and drought conditions characteristic of maritime pine habitats , may have driven unique adaptations in the catalytic properties of P. pinaster 70 kDa PPIase.

A comparative analysis might reveal patterns such as: