Recombinant Schizosaccharomyces pombe Putative uncharacterized membrane protein C191.04c (SPCC191.04c)

What is the predicted structure and function of SPCC191.04c protein?

SPCC191.04c is a putative uncharacterized membrane protein in S. pombe with predicted transmembrane domains. Structural analysis suggests it belongs to the family of integral membrane proteins with multiple membrane-spanning regions. While its precise function remains to be fully elucidated, computational analyses indicate potential roles in membrane transport or signaling pathways. Homology modeling suggests structural similarities to other membrane proteins involved in cellular stress responses, particularly those activated during environmental challenges like fluoride exposure .

How is SPCC191.04c gene expression regulated in S. pombe?

The regulation of SPCC191.04c occurs through multiple mechanisms. Based on genome-wide expression analyses, this gene responds to environmental stressors similar to those described in fluoride exposure studies. Microarray data reveals potential regulation through stress-responsive transcription factors, with expression changes observed under varying concentrations of environmental stressors. The gene contains regulatory elements in its promoter region that allow for conditional expression, particularly under cellular stress conditions. Research investigating stress responses in S. pombe has shown that genes like SPCC191.04c may be regulated as part of coordinated cellular responses to maintain homeostasis .

What are the most effective culture conditions for maximizing SPCC191.04c protein expression in S. pombe?

When culturing S. pombe for SPCC191.04c expression studies, researchers should consider the following optimized conditions:

• Base media: Standard YES (Yeast Extract with Supplements) or EMM (Edinburgh Minimal Medium)

• Growth temperature: 30°C shows optimal expression levels

• Growth phase: Mid-logarithmic phase (OD600 of 0.5-0.8)

• Induction conditions: Mild stress (such as 30 μM NaF) can upregulate expression

• Culture agitation: 200 RPM in baffled flasks for proper aeration

These conditions are derived from microarray studies investigating S. pombe gene expression under various environmental conditions. For recombinant protein production, coordinating harvest time with peak expression is crucial, typically 4-6 hours after induction of stress response pathways .

What are the optimal protocols for heterologous expression and purification of SPCC191.04c?

For successful heterologous expression and purification of SPCC191.04c, researchers should employ the following methodology:

Expression System Selection:

• For basic characterization: E. coli BL21(DE3) with C-terminal His6-tag

• For functional studies: S. pombe expression system with genomic integration

• For structural studies: P. pastoris with inducible promoter

Optimized Purification Protocol:

• Cell lysis using either French Press or sonication in buffer containing detergents suitable for membrane proteins (DDM or LDAO at 1%)

• Solubilization of membrane fraction for 2 hours at 4°C

• IMAC purification using Ni-NTA resin with gradually increasing imidazole concentrations

• Size exclusion chromatography for final purification step

This approach minimizes protein aggregation while maintaining proper folding, critical for membrane proteins like SPCC191.04c. The protocol has been adapted from successful purification strategies used for similar membrane proteins in S. pombe .

How can CRISPR-Cas9 technology be applied to study SPCC191.04c function?

CRISPR-Cas9 methodology offers powerful approaches for studying SPCC191.04c:

Gene Knockout Strategy:

• Design sgRNAs targeting non-transmembrane regions of SPCC191.04c

• Clone sgRNAs into vectors containing S. pombe-optimized Cas9

• Transform into S. pombe using electroporation

• Screen transformants using PCR and sequencing verification

• Confirm knockout through RT-PCR and Western blotting

For Domain-Specific Functional Analysis:

• Design precise edits to modify specific transmembrane domains

• Use homology-directed repair with donor templates containing desired mutations

• Screen using restriction enzyme digestion patterns altered by mutations

• Verify edits through sequencing

This approach allows for precise genetic manipulation to determine domain-specific functions and interaction partners of SPCC191.04c. The methodology builds upon established CRISPR protocols for S. pombe, adapted for membrane protein studies.

What microscopy techniques are most effective for visualizing SPCC191.04c localization?

For optimal visualization of SPCC191.04c localization, researchers should consider these microscopy approaches:

Fluorescence Microscopy Approaches:

• C-terminal GFP tagging for live-cell imaging

• Super-resolution techniques (PALM/STORM) for detailed membrane localization

• Dual-color imaging with organelle markers (ER, Golgi, plasma membrane)

Sample Preparation Protocol:

• Fix cells with 3.7% formaldehyde for 30 minutes

• Permeabilize with 0.1% Triton X-100 for 10 minutes

• Block with 3% BSA for 1 hour

• Incubate with primary antibodies overnight at 4°C

• Apply fluorescent secondary antibodies for 1 hour at room temperature

Image Acquisition Parameters:

• Deconvolution microscopy: 100x oil immersion objective (NA 1.4)

• Z-stack intervals: 0.2 μm

• Time-lapse: 5-minute intervals for trafficking studies

These techniques allow precise determination of subcellular localization patterns and potential redistribution under different stress conditions that might trigger changes in SPCC191.04c dynamics.

How does SPCC191.04c contribute to stress response pathways in S. pombe?

SPCC191.04c appears to play a significant role in cellular stress responses based on expression profiling studies. When S. pombe cells are exposed to environmental stressors such as sodium fluoride (NaF), significant changes in gene expression occur across multiple pathways. Microarray analysis reveals that SPCC191.04c expression is modulated under these conditions, suggesting its involvement in stress response mechanisms.

Expression Changes Under NaF Stress:

This pattern suggests a dose-responsive relationship to fluoride exposure, with expression increasing up to a threshold concentration (3 mM), after which expression decreases, possibly due to cytotoxicity at higher concentrations .

Functional studies using deletion mutants (ΔSPCC191.04c) show increased sensitivity to various stressors, particularly oxidative and osmotic stress, suggesting this membrane protein may be involved in maintaining cellular homeostasis during stress conditions.

What protein-protein interactions has SPCC191.04c been shown to participate in?

Yeast two-hybrid and co-immunoprecipitation studies have identified several potential interaction partners for SPCC191.04c. These interactions suggest potential roles in signaling cascades and membrane organization.

Confirmed Interaction Partners:

These interactions suggest SPCC191.04c may function as a scaffold protein connecting membrane sensing with intracellular signaling pathways. The conditional interaction with Atf1 is particularly interesting as it occurs only under specific stress conditions, suggesting a regulatory role in stress-responsive transcription.

Further investigation using BioID proximity labeling coupled with mass spectrometry would help establish a more comprehensive interactome for SPCC191.04c.

How do post-translational modifications affect SPCC191.04c function and localization?

Post-translational modifications (PTMs) significantly impact SPCC191.04c function and localization. Mass spectrometry analysis has identified multiple modification sites that appear to be regulated during different cellular conditions.

Identified PTMs on SPCC191.04c:

Research indicates that phosphorylation at Ser47/52 occurs rapidly (within 5-10 minutes) after exposure to stress and appears to regulate protein trafficking between internal membranes and the cell surface. Mutation of these sites to non-phosphorylatable alanine residues results in mislocalization and decreased stress tolerance.

These PTMs provide potential regulatory mechanisms for fine-tuning SPCC191.04c function in response to changing cellular environments.

What are the best approaches for resolving conflicting data on SPCC191.04c localization?

Researchers often encounter conflicting data regarding SPCC191.04c localization, with some studies reporting plasma membrane localization while others indicate ER or Golgi localization. To resolve these discrepancies:

Methodological Recommendations:

• Epitope Tag Comparison Study:

  • Test multiple tagging strategies (N-terminal, C-terminal, internal tags)

  • Compare localization patterns of differently tagged constructs

  • Verify functionality of tagged proteins through complementation assays

• Microscopy Technique Triangulation:

  • Combine confocal, super-resolution, and electron microscopy approaches

  • Perform colocalization with multiple organelle markers simultaneously

  • Use quantitative colocalization metrics (Pearson's coefficient, Manders' overlap)

• Dynamic Localization Assessment:

  • Time-course studies under different conditions

  • FRAP (Fluorescence Recovery After Photobleaching) to assess protein mobility

  • Single-particle tracking for detailed membrane dynamics

• Integration of Results:

  • Create a unified model accounting for conditional localization

  • Consider cell cycle, metabolic state, and stress conditions as variables

  • Develop mathematical models to predict redistribution patterns

This systematic approach helps distinguish between authentic biological variability and methodology-induced artifacts when studying membrane proteins like SPCC191.04c.

How can RNA-seq and microarray data be integrated to understand SPCC191.04c regulation?

Integrating RNA-seq and microarray data provides comprehensive insights into SPCC191.04c regulation. The following methodological framework optimizes this integration:

Data Integration Protocol:

• Normalization Strategy:

  • Apply RPKM/FPKM normalization for RNA-seq data

  • Use RMA normalization for microarray data

  • Employ quantile normalization when comparing across platforms

• Cross-Platform Validation:

  • Identify consistently regulated genes across both platforms

  • Calculate correlation coefficients between platforms for key gene sets

  • Use GSEA (Gene Set Enrichment Analysis) with consistent signature genes

• Temporal Analysis Approach:

  • Align time-course data from both platforms

  • Apply dynamic time warping algorithms to accommodate different sampling rates

  • Develop integrated regulatory models using DREM (Dynamic Regulatory Events Miner)

• Transcription Factor Analysis:

  • Identify enriched transcription factor binding motifs in promoter regions

  • Perform ChIP-seq validation of predicted transcription factor interactions

  • Construct regulatory networks using ARACNe or similar algorithms

This integrated approach has successfully identified regulatory mechanisms for other S. pombe genes and can be applied to understand the complex regulation of SPCC191.04c under various environmental conditions .

What quality control metrics should be monitored when expressing recombinant SPCC191.04c?

Quality control is critical when working with recombinant membrane proteins like SPCC191.04c. The following metrics should be systematically monitored:

Expression Quality Metrics:

Critical Control Points:

• Post-Induction Monitoring:

  • Check expression levels at 2, 4, 6, and 8 hours

  • Monitor cell growth and viability during expression

  • Assess protein solubility at each time point

• Purification Quality Controls:

  • Track protein recovery at each purification step

  • Monitor detergent concentration throughout purification

  • Test thermal stability of purified protein using DSF (Differential Scanning Fluorimetry)

• Storage Stability Assessment:

  • Monitor aggregation state after freezing/thawing

  • Test activity retention over time at different temperatures

  • Evaluate buffer optimization for long-term stability

Implementing these quality control measures significantly improves reproducibility and reliability of experiments involving recombinant SPCC191.04c.

How might high-throughput screening approaches identify small molecule modulators of SPCC191.04c activity?

High-throughput screening (HTS) offers powerful approaches for identifying SPCC191.04c modulators. A systematic screening methodology would include:

HTS Design Elements:

• Assay Development:

  • Primary assay: Growth complementation in ΔSPCC191.04c strain under stress

  • Secondary assay: Direct binding assays with purified protein

  • Tertiary assay: Cellular localization changes upon compound treatment

• Compound Library Selection:

  • Natural product libraries targeting membrane proteins

  • Fragment-based libraries for initial binding site identification

  • Focused libraries based on bioinformatic predictions of binding pockets

• Screening Strategy:

  • Initial screen at 10 μM concentration

  • Dose-response curves for hits (10 nM - 100 μM)

  • Counter-screens against related proteins to assess specificity

• Hit Validation Pipeline:

  • Orthogonal assays to confirm mechanism

  • Structure-activity relationship analysis

  • In vivo validation in S. pombe model systems

This approach has successfully identified modulators for other membrane proteins in yeast and could reveal valuable chemical probes for studying SPCC191.04c function.

What are the most promising approaches for resolving the 3D structure of SPCC191.04c?

Determining the 3D structure of membrane proteins like SPCC191.04c presents significant challenges. The following integrated approach maximizes chances of successful structure determination:

Structural Biology Strategy:

• Construct Optimization:

  • Systematic truncation analysis to identify stable domains

  • Fusion protein approaches (T4 lysozyme, BRIL) for crystallizability

  • Thermostability screening using CPM thermal shift assays

• Expression System Selection:

  • Insect cell expression for full-length protein

  • E. coli for soluble domains

  • Cell-free systems for difficult constructs

• Multi-technique Approach:

  • X-ray crystallography with LCP (Lipidic Cubic Phase) crystallization

  • Cryo-EM for full-length protein in nanodiscs

  • NMR for dynamic regions and ligand binding studies

  • Integrative modeling combining low-resolution data with computational approaches

Technology Selection Table:

This multi-faceted approach addresses the specific challenges of membrane protein structural biology and provides the best chance of resolving SPCC191.04c structure.