Recombinant Photosystem II reaction center protein H (psbH)

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Description

Definition and Biological Role of Recombinant Photosystem II Reaction Center Protein H (psbH)

Recombinant Photosystem II reaction center protein H (psbH) is a genetically engineered version of the psbH-encoded protein, a critical subunit of Photosystem II (PSII) in oxygenic photosynthetic organisms. PSII is a multi-subunit complex responsible for water splitting and oxygen evolution during photosynthesis . PsbH, a low-molecular-mass (LMM) transmembrane protein (~9–10 kDa), stabilizes PSII structure and facilitates its assembly, repair, and dimerization .

Molecular Features

  • Sequence: PsbH contains a conserved N-terminal threonine residue (Thr3 in Chlamydomonas reinhardtii) critical for phosphorylation .

  • Topology: Single transmembrane helix with stromal-facing phosphorylation sites .

  • Interactions: Binds CP47 (PsbB) and D2 (PsbD) subunits, and associates with assembly factors like Psb34 .

Functional Roles

  1. PSII Assembly: Incorporates during the transition from RC47a to RC47b complexes, stabilizing early assembly intermediates .

  2. Photoprotection: Phosphorylation at Thr3 modulates PSII repair under high-light stress .

  3. Dimerization: Essential for PSII core dimer formation .

Table 1: Experimental Insights into PsbH Function

Study ModelKey FindingsSource
Chlamydomonas reinhardtii (psbH knockout)PSII-deficient phenotype; rapid turnover of D1/D2/CP43/CP47 proteins .
Arabidopsis thaliana (PPL1 mutant)Delayed PSII repair linked to PsbH phosphorylation .
Cyanobacterial PSIIPsbH binds CP47 near cytochrome b559, preventing photodamage during assembly .
Thr3 → Ala mutationRetains PSII activity but impairs repair under high light .

Phosphorylation Dynamics

  • Mechanism: Light-dependent phosphorylation at Thr3 regulates PSII disassembly and migration to repair sites .

  • Consequence: Non-phosphorylatable mutants (e.g., T3A) show impaired recovery from photoinhibition .

Research Applications

  1. Assembly Studies: Used to probe PSII intermediate complexes (e.g., RC47b) .

  2. Post-Translational Modification Analysis: Phosphorylation mutants elucidate repair mechanisms .

  3. Antibody Production: Recombinant PsbH serves as an antigen for antibody generation .

Challenges and Future Directions

  • Structural Resolution: Cryo-EM studies of recombinant PsbH-bound PSII intermediates remain limited .

  • Phosphorylation Crosstalk: Interactions with kinases (e.g., STN8) and phosphatases require further exploration .

  • Biotechnological Potential: Engineered PsbH variants could enhance crop resilience to photoinhibition .

Product Specs

Form
Lyophilized powder
Please note: We prioritize shipping the format currently in stock. However, if you require a specific format, please indicate your preference in the order notes, and we will prepare accordingly.
Lead Time
Delivery time may vary depending on the purchasing method or location. Please consult your local distributors for specific delivery timelines.
Note: All protein shipments are sent with standard blue ice packs. If you require dry ice shipping, please inform us in advance as additional fees will apply.
Notes
Repeated freezing and thawing is not recommended. Store working aliquots at 4°C for up to one week.
Reconstitution
We recommend briefly centrifuging the vial before opening to ensure the contents settle to the bottom. Reconstitute the protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL. We recommend adding 5-50% glycerol (final concentration) and aliquoting for long-term storage at -20°C/-80°C. Our standard final concentration of glycerol is 50%. Customers may use this as a reference.
Shelf Life
Shelf life is influenced by various factors, including storage conditions, buffer components, storage temperature, and the inherent stability of the protein.
Generally, the shelf life of liquid form is 6 months at -20°C/-80°C. The shelf life of lyophilized form is 12 months at -20°C/-80°C.
Storage Condition
Upon receipt, store at -20°C/-80°C. Aliquoting is necessary for multiple uses. Avoid repeated freeze-thaw cycles.
Tag Info
Tag type is determined during the manufacturing process.
The tag type is decided during production. If you have a specific tag type requirement, please inform us, and we will prioritize developing it accordingly.
Synonyms
psbH; Photosystem II reaction center protein H; PSII-H
Buffer Before Lyophilization
Tris/PBS-based buffer, 6% Trehalose.
Datasheet
Please contact us to get it.
Expression Region
1-64
Protein Length
full length protein
Species
Prochlorothrix hollandica
Target Names
psbH
Target Protein Sequence
MGQKTALSNFLKPFNSNAGKVVPGWGTTPLMGLFMGLLFVFLLIILQIYNSTIVLDAFSV NVGG
Uniprot No.

Target Background

Function
Photosystem II (PSII) reaction center protein H (psbH) is a crucial component of the PSII core complex. Its presence is essential for the stability and assembly of PSII. PSII is a light-driven water:plastoquinone oxidoreductase that harnesses light energy to extract electrons from water, producing oxygen and a proton gradient, which is then utilized for ATP formation. This complex process involves a core antenna complex that captures photons and an electron transfer chain responsible for converting photonic excitation into charge separation.
Protein Families
PsbH family
Subcellular Location
Cellular thylakoid membrane; Single-pass membrane protein.

Q&A

What is the structural position of psbH within the PSII complex?

  • Cryo-electron microscopy techniques similar to those used for RCII complex characterization

  • Cross-linking studies to identify protein-protein interaction interfaces

  • Comparative structural analysis across cyanobacteria, algae, and plants

The RCII complex, formed from D1mod and D2mod association, has been successfully isolated from Synechocystis strains and structurally characterized, providing a methodological framework for studying associated proteins like psbH .

How does psbH contribute to PSII function and stability?

psbH appears to function in maintaining PSII stability, particularly during stress conditions and repair cycles. From a methodological perspective, researchers should:

  • Generate knockout/knockdown mutants to assess functional consequences

  • Perform site-directed mutagenesis of conserved residues

  • Measure photochemical parameters under various light and stress conditions

  • Assess PSII assembly kinetics with and without functional psbH

Similar to the HliC/D pairs that play photoprotective roles by dissipating absorbed energy, psbH may contribute to stability through specific protein-protein interactions that help maintain optimal configuration of the complex .

What expression systems are most effective for recombinant psbH production?

For effective recombinant production of psbH, researchers should consider:

  • Bacterial systems (E. coli) for high-yield expression, though proper folding may be challenging

  • Cyanobacterial hosts for more native-like membrane integration

  • Cell-free expression systems for difficult-to-express membrane proteins

Table 1. Comparison of Expression Systems for Recombinant psbH

Expression SystemAdvantagesLimitationsOptimal Purification Method
E. coliHigh yield, rapid growthMay form inclusion bodiesDetergent extraction, His-tag purification
CyanobacteriaNative-like foldingLower yield, slower growthMembrane fractionation, affinity chromatography
Cell-freeControl over redox environmentHigher cost, lower scaleDirect purification from reaction mixture

Each system requires optimization of codon usage, purification tags, and membrane protein extraction protocols to maintain structural integrity.

How can causal mechanisms of psbH function be identified experimentally?

Identifying causal mechanisms requires specially designed experiments that distinguish correlation from causation. Researchers should consider:

  • Single-experiment designs where only psbH expression is manipulated

  • Parallel designs where subjects are randomly assigned to experiments manipulating either just psbH or both psbH and potential mediator proteins

  • Crossover designs where experimental units are sequentially assigned to different conditions

These approaches help determine whether observed effects are directly caused by psbH or mediated through other components of the photosynthetic apparatus . For instance, to determine if psbH directly affects PSII stability or works through interaction with other proteins, researchers might compare direct psbH manipulation with manipulation of both psbH and potential partner proteins.

What techniques are most effective for studying psbH interactions with other PSII components?

Researchers should employ multiple complementary approaches:

  • Co-immunoprecipitation with tagged psbH to identify interaction partners

  • Yeast two-hybrid or bacterial two-hybrid screening

  • Förster resonance energy transfer (FRET) for in vivo interaction analysis

  • Chemical cross-linking followed by mass spectrometry

For membrane proteins like those in PSII, careful consideration of detergent selection is crucial, as improper solubilization can disrupt native interactions. When manipulating psbH to study interactions, researchers must consider whether manipulations might affect PSII function through pathways other than those directly involving psbH .

How can encouragement designs overcome challenges in direct psbH manipulation?

When direct manipulation of psbH is challenging or disruptive to normal function, researchers can implement encouragement designs:

  • Create conditions that encourage or discourage certain psbH conformations or interactions

  • Use genetic backgrounds that alter psbH expression without completely eliminating it

  • Apply chemical approaches that modify psbH function indirectly

In these designs, experimental subjects are "randomly encouraged to take (rather than assigned to) certain values of the mediator" . This approach is particularly valuable for studying dynamic processes like PSII assembly or repair, where direct manipulation might fundamentally alter the system being studied.

How can contradiction analysis help resolve challenges in psbH structural studies?

TRIZ-based contradiction analysis offers a systematic approach to resolving research challenges:

  • Identify the improving parameter (e.g., structural detail) and worsening parameter (e.g., protein stability during isolation)

  • Consult the contradiction matrix to identify potential resolution approaches

  • Implement inventive principles to design new experimental approaches

Table 2. Example Contradictions in psbH Research and Resolution Approaches

Improving ParameterWorsening ParameterPotential Resolution Approach
Isolation purityNative structure preservationUse nested doll principle: create fusion construct that shields native structure
Expression yieldProper foldingBeforehand cushioning: optimize chaperone co-expression
Functional assessmentMembrane integrationParameter change: develop in vitro assays that mimic membrane environment

This approach frames technical problems using parameters that either improve or worsen system conditions, helping researchers identify creative solutions to seemingly intractable problems .

What statistical approaches are appropriate for analyzing psbH functional data?

The choice of statistical analysis depends on experimental design:

  • For comparative studies (wild-type vs. mutant), use t-tests when data is normally distributed

  • For more complex designs with multiple variables, employ ANOVA or regression analysis

  • For time-series data on PSII assembly or repair, consider mixed-effects models

In the experimental study described in search result , t-tests were used to analyze pre-test and post-test data in control and treatment groups. Similar approaches can be adapted for psbH studies, with careful attention to sample size, data distribution, and effect size reporting .

How can LLM-augmented tools support analysis of contradictions in psbH literature?

Large language models (LLMs) like GPT-4 can assist in analyzing complex research problems:

  • Systematic identification of contradictions across multiple papers

  • Analysis of methodological differences that might explain contradictory results

  • Generation of hypotheses that could reconcile apparently conflicting findings

When applied to contradiction analysis in TRIZ methodology, GPT-4 demonstrated varying levels of precision and recall, suggesting these tools can provide valuable support while requiring expert oversight . For psbH research, where literature may contain seemingly contradictory findings due to different experimental systems or conditions, such tools could help researchers synthesize knowledge more effectively.

What role does psbH play in the biogenesis and assembly of PSII complexes?

The assembly of PSII involves a coordinated process of protein insertion, cofactor binding, and complex formation. When investigating psbH's role:

  • Study temporal dynamics of psbH incorporation using pulse-chase experiments

  • Create assembly-impaired mutants to identify rate-limiting steps

  • Analyze intermediate complexes that accumulate in the absence of psbH

Similar to how the HliC/D pair and Ycf39 affect incorporation of newly synthesized D1 into PSII under high light conditions, psbH may facilitate specific assembly steps or stabilize intermediate complexes . Researchers should design experiments that can distinguish between direct structural roles and regulatory or chaperon-like functions.

How does psbH contribute to PSII repair mechanisms under high light stress?

High light conditions damage PSII components, particularly the D1 protein, necessitating repair processes. To study psbH's role:

  • Compare repair kinetics in wild-type and psbH-deficient systems

  • Analyze protein turnover rates using isotope labeling

  • Assess localization of psbH during repair processes

  • Measure photoprotection capacity with and without functional psbH

The photoprotective role observed for HliC/D pairs, which "play a photoprotective role in dissipating energy absorbed by RCII," provides a model for investigating potential similar roles for psbH .

What experimental approaches best address contradictory findings in psbH research?

When research results appear contradictory, consider:

  • Implementing multiple experimental designs to identify which findings are robust

  • Systematically varying experimental conditions to identify context-dependent effects

  • Developing mathematical models that can reconcile apparently contradictory observations

Using approaches from causal mechanism research, researchers can determine whether contradictions arise from different mediating factors across experimental systems . The parallel and crossover designs described in search result are particularly valuable for resolving such contradictions, as they allow researchers to identify context-specific effects that might explain different outcomes across studies.

How might cryo-EM advances improve our understanding of psbH structure and function?

Recent structural biology advances offer new opportunities:

  • Higher-resolution structures of PSII with identifiable psbH positioning

  • Time-resolved cryo-EM to capture different states during assembly/repair

  • Visualization of conformational changes induced by different conditions

Similar to how cryo-EM has been used to determine the structure of the RCII complex , advancing techniques could reveal previously unobservable details about psbH integration and interactions within the PSII complex.

What novel genetic approaches could enhance psbH functional studies?

Emerging genetic technologies provide powerful new tools:

  • CRISPR-Cas9 for precise genomic modification in photosynthetic organisms

  • Optogenetic control of psbH expression or activity

  • Multiplexed mutagenesis to create comprehensive mutation libraries

Table 3. Emerging Genetic Approaches for psbH Research

ApproachApplication in psbH ResearchTechnical Considerations
CRISPR-Cas9Precise modification of psbH sequence or regulatory elementsPAM site availability, transformation efficiency
OptogeneticsLight-controlled expression or activity of psbHSpectral overlap with photosynthetic pigments
Multiplexed MutagenesisComprehensive functional mapping of psbH domainsHigh-throughput screening capabilities

These approaches enable more precise manipulation and analysis than traditional genetic methods, potentially resolving longstanding questions about psbH function.

How can problem-solving frameworks like TRIZ be systematically applied to advance psbH research?

The TRIZ problem-solving methodology offers a structured approach:

  • Frame research challenges as specific contradictions

  • Identify improving and worsening parameters

  • Apply the contradiction matrix and inventive principles to develop novel approaches

This methodology transforms "a concrete problem" into a "TRIZ problem," which then evolves into a "TRIZ solution" and finally a "concrete solution" . By applying this framework, researchers can develop innovative approaches to challenging aspects of psbH research, particularly where traditional methods have proven insufficient.

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