Recombinant Sulfolobus islandicus UPF0290 protein M164_1356 (M164_1356)

What are the optimal growth conditions for Sulfolobus islandicus?

Sulfolobus islandicus is an extremophilic archaeon that thrives in high-temperature, acidic environments. For laboratory cultivation, the optimal growth conditions include:

• Temperature: 75-78°C

• Growth media options:

  • GCVy medium (containing basic salts supplemented with 0.2% glucose, 0.2% Casamino Acids, and 0.005% yeast extract plus a vitamin mixture)

  • SCVy medium (containing basic salts supplemented with 0.2% sucrose, 0.2% Casamino Acids, and 0.005% yeast extract plus a vitamin mixture)

  • DT liquid medium (Dextrin/EZMix N-Z-Amine A)

For solid media preparation, 2× concentrated DT medium supplemented with 20 mM MgSO₄ and 7 mM CaCl₂·2H₂O mixed in equal volumes with 1.4% (w/v) Gelrite is commonly used . For selective growth, the medium can be supplemented with 20 μg/ml uracil, 50 μg/ml agmatine, and 50 μg/ml 5-Fluoroorotic Acid (5-FOA) . For recombinant protein expression, cells can be transferred to ACVy medium where d-arabinose substitutes for other sugars to elevate protein production .

What expression systems are available for producing recombinant S. islandicus proteins?

Several expression systems have been developed for S. islandicus, leveraging its unique properties as a hyperthermophilic host:

• Arabinose-inducible promoter system: The araS promoter confers high levels of expression to reporter genes in S. islandicus . This system allows controlled induction of protein expression by transferring cells to medium containing d-arabinose.

• Constitutive promoter systems: Promoters such as that of the Sac7d gene from Sulfolobus acidocaldarius DSM639 have been used for constitutive expression .

• Shuttle vector systems: Various plasmid-based shuttle vectors, such as pZC1, facilitate gene expression in S. islandicus .

• Chromosomal integration systems: Recent advances have identified multiple chromosomal integration sites in S. islandicus that allow stable expression of heterologous genes . These sites have been characterized using the lacS (β-galactosidase) reporter system to assess their suitability for gene expression.

The choice between these systems depends on specific experimental requirements, including whether temporal control of expression is needed and the desired expression level of the target protein.

What methods are available for verifying recombinant UPF0290 protein expression?

Verification of recombinant UPF0290 protein M164_1356 expression requires approaches suitable for thermostable proteins:

• β-galactosidase reporter assays: When using lacS as a reporter gene fused to the protein of interest, activity can be measured through standardized protocols involving cell sonication and enzymatic assays .

• SDS-PAGE analysis: The expressed protein can be visualized on polyacrylamide gels, with an expected size corresponding to the 166 amino acids plus any tags included in the expression construct.

• Western blotting: Using antibodies against the protein or fusion tags incorporated into the recombinant construct.

• Mass spectrometry: For definitive identification and confirmation of the protein's amino acid sequence and post-translational modifications.

• Thermal stability assays: Given the hyperthermophilic origin of the protein, thermal shift assays can confirm proper folding and stability at high temperatures.

For S. islandicus proteins, cell lysis protocols typically involve sonication (4 min and 30 sec with a 30-sec on, 10-sec off pulse cycle at 25% amplitude) followed by centrifugation (15,000 rpm for 10 min) to obtain the cleared lysate for analysis .

What bioinformatic approaches can predict the function of UPF0290 protein M164_1356?

Since UPF0290 protein M164_1356 belongs to an uncharacterized protein family, several bioinformatic approaches can help predict its potential functions:

• Sequence analysis and motif identification: Analyzing the amino acid sequence reveals potential functional domains or motifs. The sequence suggests membrane association based on hydrophobic regions .

• Structural prediction: Contemporary tools like AlphaFold can predict the protein's 3D structure, potentially revealing structural similarities to proteins of known function.

• Genomic context analysis: Examining genes located near M164_1356 in the S. islandicus genome may provide insights into functional relationships and potential operon structures.

• Comparative genomics: Analyzing the conservation and distribution of this gene across archaeal species can indicate its evolutionary importance.

• Essential gene analysis: Determining whether M164_1356 is part of the essential genome of S. islandicus provides clues about its biological significance .

These computational approaches generate hypotheses that must be validated through experimental characterization to establish the protein's function in S. islandicus biology.

How can expression of thermostable proteins like UPF0290 be optimized in S. islandicus?

Optimizing the expression of thermostable proteins in S. islandicus requires consideration of several factors specific to hyperthermophilic archaea:

• Promoter selection: The arabinose-inducible araS promoter has demonstrated high expression levels in S. islandicus . For UPF0290 protein, this inducible system allows controlled expression and potential mitigation of toxicity effects.

• Integration site selection: Research has identified and characterized 13 artificial CRISPR RNAs (crRNAs) targeting eight chromosomal integration sites in S. islandicus . These sites show significant positional effects on expression levels, allowing researchers to fine-tune expression by selecting appropriate integration locations.

• Growth conditions optimization:

  • Temperature: Maintain cultures at 75-78°C for optimal growth

  • Media composition: For inducible systems, transition from SCVy to ACVy medium where d-arabinose replaces sucrose to induce protein expression

  • Growth phase: Harvest cells at appropriate growth phase, typically mid-log phase (OD₆₀₀ of 0.2-0.3)

• Genetic background consideration: Utilizing S. islandicus strains with specific mutations (e.g., ΔpyrEF and ΔlacS) can improve heterologous protein production by eliminating competing pathways and providing selection markers .

• Expression monitoring: Implementing a reporter system, such as β-galactosidase assays, allows quantitative monitoring of expression levels under different conditions .

By systematically optimizing these parameters, researchers can achieve higher yields and better functional expression of thermostable proteins like UPF0290 in S. islandicus.

What challenges exist in purifying recombinant proteins from hyperthermophilic archaea?

Purifying recombinant proteins from hyperthermophilic archaea like S. islandicus presents unique challenges that require specialized approaches:

• Cell lysis considerations:

  • Standard sonication protocols may need modification for efficient lysis of archaeal cells

  • Recommended protocol: Sonication using a Q125 sonicator (4 min and 30 sec with a 30-sec on, 10-sec off pulse cycle at 25% amplitude)

  • Alternative methods include high-pressure homogenization or specific detergent-based lysis buffers

• Thermostability advantages:

  • Heat treatment (60-70°C) of cell lysates can be used as an initial purification step, as many contaminating proteins will denature while S. islandicus proteins remain soluble

  • This approach can significantly reduce host protein contamination

• Buffer considerations:

  • Use Tris-based buffers with pH 8.0 for initial resuspension

  • Consider adding glycerol (up to 50%) for long-term storage

  • Avoid repeated freeze-thaw cycles, which can affect protein stability

• Membrane protein extraction:

  • For membrane-associated proteins like UPF0290, additional considerations for detergent selection and membrane fractionation are necessary

  • The hydrophobic nature of the protein (as indicated by its sequence) suggests it may require specialized extraction methods

• Storage conditions:

  • Store at -20°C for standard conditions, or -80°C for extended storage

  • Working aliquots can be maintained at 4°C for up to one week to avoid freeze-thaw cycles

These specialized approaches leverage the inherent thermostability of proteins like UPF0290 M164_1356, providing significant purification advantages compared to proteins from mesophilic organisms.

How can the structural stability of UPF0290 protein M164_1356 be assessed at different temperatures?

Assessing the structural stability of UPF0290 protein M164_1356 across a temperature range requires specialized techniques suitable for thermostable proteins:

• Differential Scanning Calorimetry (DSC):

  • Measures heat capacity changes during protein unfolding

  • Can determine the melting temperature (Tm) and provide thermodynamic parameters

  • Particularly useful for hyperthermophilic proteins with high melting points

  • Experimental setup should allow measurements at temperatures up to 120°C

• Circular Dichroism (CD) Spectroscopy:

  • Monitors changes in secondary structure as a function of temperature

  • Requires specialized high-temperature CD cells

  • Can provide insights into structural transitions during heating/cooling cycles

• Intrinsic Fluorescence Spectroscopy:

  • Exploits the presence of aromatic residues (particularly the tyrosine and tryptophan residues present in the UPF0290 sequence)

  • Changes in fluorescence intensity or emission maxima indicate conformational changes

  • Can be performed at various temperatures to generate stability curves

• Activity-based stability assessments:

  • Once a functional assay is developed for UPF0290, measuring activity retention after heat treatment

  • Can provide insights into functional stability that may differ from structural stability

When interpreting results, it's important to consider that as a protein from a hyperthermophile, UPF0290 protein M164_1356 may show unusual stability profiles and potentially multiple transition states during unfolding, reflecting its adaptation to extreme conditions.

What genetic tools are available for manipulating the M164_1356 gene in S. islandicus?

Several sophisticated genetic tools have been developed specifically for S. islandicus that can be applied to manipulate the M164_1356 gene:

• CRISPR-Cas-based genome editing:

  • S. islandicus possesses endogenous CRISPR-Cas systems that can be harnessed for genome editing

  • The CRISPR-COPIES pipeline has been used to identify and characterize artificial CRISPR RNAs (crRNAs) for targeting specific sites

  • This approach allows precise deletion, modification, or replacement of the M164_1356 gene

• Marker-based selection systems:

  • Nutritional markers such as pyrEF and argD allow for selection of transformants

  • Counter-selection using 5-Fluoroorotic Acid (5-FOA) enables marker recycling

  • Example workflow: Create a knockout strain using pyrEF marker, then counter-select using 5-FOA

• Expression plasmids and shuttle vectors:

  • Plasmids like pZC1 can be used for heterologous expression

  • Various promoters (araS, Sac7d) provide options for constitutive or inducible expression

  • The SSV1 T6 terminator has been used successfully in expression constructs

• Reporter systems:

  • The lacS (β-galactosidase) reporter system allows for monitoring gene expression

  • This system has been successfully used to characterize chromosomal integration sites in S. islandicus

• Transposon mutagenesis systems:

  • Modified in vitro transposon mutagenesis systems derived from Tn5 have been established for S. islandicus

  • This approach allows for genome-wide disruption libraries and identification of essential genes

These tools collectively provide a comprehensive toolkit for manipulating M164_1356 in its native host and studying its expression, regulation, and function.

How does the essential genome analysis of S. islandicus inform functional studies of UPF0290 protein M164_1356?

The essential genome analysis of S. islandicus provides valuable context for studying UPF0290 protein M164_1356:

• Essentiality determination:

  • Genome-wide disruption libraries in S. islandicus have identified the repertoire of essential genes

  • The M164_1356 gene can be classified as either essential or non-essential based on its tolerance to transposon insertion

  • This classification provides fundamental insights into its biological importance

• Functional contextualization:

  • Essential genes often participate in core cellular processes, while non-essential genes may have specialized or redundant functions

  • Determining where M164_1356 fits in this spectrum guides hypotheses about its function

• Evolutionary significance:

  • The phyletic distribution of M164_1356 within the TACK superphylum can illustrate potential evolutionary transitions

  • Comparison with essential gene sets from other archaea highlights conservation patterns that may indicate functional importance

• Experimental design guidance:

  • For essential genes, conditional depletion strategies rather than knockout approaches would be required

  • For non-essential genes, knockout phenotyping can provide functional insights

• Integration with other datasets:

  • Correlation of essentiality data with transcriptomic and proteomic profiles

  • Analysis of genetic interactions with other genes in the S. islandicus genome

This integration of essential genome data with targeted studies of UPF0290 protein M164_1356 can significantly accelerate functional characterization by providing a systems-level context for interpreting experimental results.

What protocols are recommended for extracting thermostable proteins from S. islandicus?

Extracting thermostable proteins from S. islandicus requires specialized protocols that account for the unique properties of archaeal cells and hyperthermophilic proteins:

• Cell harvesting and preparation:

  • Grow S. islandicus cultures to mid-log phase (OD₆₀₀ of 0.2-0.3)

  • Harvest cells by centrifugation at 4000 rpm for 20 minutes

  • Wash cell pellet with a suitable buffer (e.g., 10 mM Tris-HCl, pH 8.0)

  • Cell pellets can be stored at -20°C until processing if not used immediately

• Cell lysis methods:

  • Sonication protocol: Resuspend cells in lysis buffer (10 mM Tris-HCl, pH 8.0) and sonicate using a Q125 sonicator (4 min and 30 sec with a 30-sec on, 10-sec off pulse cycle at 25% amplitude)

  • For membrane-associated proteins like UPF0290, consider detergent-based extraction methods

• Clarification of lysate:

  • Centrifuge lysate at 15,000 rpm for 10 minutes to remove cell debris

  • For membrane proteins, additional ultracentrifugation steps may be required to separate membrane fractions

• Heat treatment advantage:

  • Exploit the thermostability of S. islandicus proteins by heating the clarified lysate (70-80°C for 20-30 minutes)

  • This step denatures most contaminating proteins while leaving thermostable proteins intact

  • Remove denatured proteins by centrifugation (15,000 rpm for 15 minutes)

• Protein storage considerations:

  • Store in Tris-based buffer with 50% glycerol for long-term stability

  • Aliquot to avoid repeated freeze-thaw cycles

  • For optimal stability, store working aliquots at 4°C for up to one week and long-term storage at -20°C or -80°C

This optimized extraction protocol leverages the inherent thermostability of proteins like UPF0290 M164_1356, providing a significant purification advantage compared to proteins extracted from mesophilic organisms.

How can experiments be designed to elucidate the function of UPF0290 protein M164_1356?

Designing experiments to determine the function of an uncharacterized protein like UPF0290 M164_1356 requires a multi-faceted approach:

• Gene knockout and phenotypic analysis:

  • Create a CRISPR-Cas-based knockout of the M164_1356 gene in S. islandicus

  • Compare growth characteristics of wild-type and knockout strains under various conditions

  • If M164_1356 is essential based on genome-wide analysis, use conditional depletion strategies

  • Analyze cellular morphology, membrane integrity, and stress responses

• Localization studies:

  • Create fluorescent protein fusions to determine subcellular localization

  • Use membrane fractionation experiments to confirm the predicted membrane association

  • Analyze temporal expression patterns during different growth phases

• Protein-protein interaction analyses:

  • Conduct pull-down assays using tagged versions of UPF0290

  • Use proximity-dependent labeling to identify neighboring proteins

  • Compare interaction partners under different environmental conditions

• Biochemical activity screening:

  • Test for common enzymatic activities

  • Assess membrane transport capabilities using liposome reconstitution

  • Investigate potential roles in stress response using thermal and chemical challenges

  • Consider the amino acid sequence features (hydrophobic regions) when designing functional assays

• Multi-omics integration:

  • Compare transcriptome alterations in knockout or depleted strains

  • Analyze metabolome changes to identify affected pathways

  • Perform comparative proteomics to detect compensatory protein expression

  • Integrate with existing essential genome data to contextualize functional importance

This systematic approach combines genetic, biochemical, and systems biology methods to generate complementary evidence regarding the function of UPF0290 protein M164_1356 in S. islandicus.

What considerations should guide the design of expression constructs for UPF0290 protein M164_1356?

Designing effective expression constructs for UPF0290 protein M164_1356 requires careful consideration of multiple factors:

• Promoter selection:

  • For inducible expression: The araS promoter provides high-level, controlled expression in S. islandicus

  • For constitutive expression: The Sac7d promoter from S. acidocaldarius has been successfully used

  • Match promoter strength to experimental requirements (structural studies may require high expression, while functional studies may benefit from near-native levels)

• Expression vector considerations:

  • Shuttle vectors like pZC1 enable flexible genetic manipulation

  • For genomic integration, consider the characterized integration sites with known expression properties

  • Include appropriate selectable markers (e.g., pyrEF) for strain construction

• Protein fusion design:

  • N-terminal vs. C-terminal tags: Consider the predicted membrane association of UPF0290

  • Tag options: Affinity tags (His, FLAG) for purification, fluorescent proteins for localization

  • Linker sequences: Flexible linkers may be needed to preserve protein function

  • Cleavage sites: Include protease recognition sequences if tag removal is desired

• Terminator selection:

  • The SSV1 T6 terminator has been successfully used in S. islandicus expression constructs

  • Ensure efficient transcription termination to maximize expression

• Codon optimization:

  • While less critical when expressing in the native organism, consider codon usage for any modified regions

  • Use the full 166 amino acid sequence for complete protein expression

• Restriction site design:

  • Common restriction sites used in S. islandicus constructs include FseI, SbfI, and PaqCI

  • Ensure selected restriction sites are not present within the M164_1356 sequence

By carefully considering these factors, researchers can create expression constructs that maximize the likelihood of obtaining functional UPF0290 protein for subsequent characterization studies.

How can β-galactosidase reporter assays be optimized for studying gene expression in S. islandicus?

The β-galactosidase (lacS) reporter system has proven effective for monitoring gene expression in S. islandicus. Optimizing this assay for maximum sensitivity and reproducibility involves several considerations:

• Cell growth and harvesting protocol:

  • Grow S. islandicus cultures to mid-log phase (OD₆₀₀ of 0.2)

  • Collect cells by centrifugation at 4000 rpm for 20 minutes

  • Resuspend in 750 μL of 10 mM Tris-HCl, pH 8.0

  • Cell resuspensions can be stored at -20°C if not processed immediately

• Cell lysis optimization:

  • Sonicate using a Q125 sonicator (4 min and 30 sec with a 30-sec on, 10-sec off pulse cycle at 25% amplitude)

  • Ensure complete lysis by microscopic examination

  • Collect supernatants following centrifugation at 15,000 rpm for 10 minutes

• Assay conditions for hyperthermophilic β-galactosidase:

  • Optimal temperature: The assay should be performed at elevated temperatures (70-75°C) to reflect the enzyme's thermophilic nature

  • Substrate concentration: Optimize ONPG (o-nitrophenyl-β-D-galactopyranoside) concentration for maximum sensitivity

  • Buffer composition: Use buffers stable at high temperatures (phosphate or Tris-based)

  • Reaction timing: Monitor the reaction kinetics to establish the linear range

• Data normalization approaches:

  • Normalize activity to total protein concentration

  • Include appropriate controls: empty vector, constitutive promoter, and uninduced samples

  • Perform measurements with at least three biological replicates for statistical validity

• Applications for studying M164_1356:

  • Create transcriptional fusions between the M164_1356 promoter and lacS

  • Test expression under different environmental conditions

  • Use deletion analysis to identify regulatory elements in the promoter region

This optimized β-galactosidase assay protocol provides a reliable method for quantitatively assessing gene expression in S. islandicus, enabling detailed studies of the regulation of genes like M164_1356.

What PCR and cloning strategies are recommended for working with M164_1356 gene?

Designing effective PCR and cloning strategies for the M164_1356 gene requires special considerations due to the extreme growth conditions of S. islandicus:

• PCR amplification recommendations:

  • Use high-fidelity, thermostable DNA polymerases suitable for GC-rich templates

  • Include DMSO (5-10%) or other PCR additives to help with potential secondary structures

  • Design primers with slightly higher melting temperatures (65-70°C)

  • PCR cycling conditions: initial denaturation at 98°C (2-3 minutes), followed by 30 cycles of 98°C (15 sec), 65°C (30 sec), 72°C (30 sec), and final extension at 72°C (5 min)

• Primer design considerations:

  • For the complete M164_1356 gene (501 bp encoding 166 amino acids) :

    • Forward primer should include 20-25 bp of the 5' region

    • Reverse primer should complement the 3' end including the stop codon

    • Add restriction sites compatible with S. islandicus vectors (e.g., FseI, SbfI, PaqCI)

    • Include 3-6 additional nucleotides at the 5' end of primers with restriction sites

• Cloning strategies:

  • For expression vectors:

    • Digest plasmid (e.g., pCYZ1) with appropriate restriction enzymes (FseI and SbfI)

    • Assemble with expression cassette containing selected promoter (araS or Sac7d)

    • Use the SSV1 T6 terminator for efficient transcription termination

    • Consider including purification tags for downstream protein isolation

• Transformation into S. islandicus:

  • Use electroporation-mediated transformation for introducing constructs

  • For plasmid elimination after confirmation of successful integration, use 5-FOA counterselection

  • Verify transformants by PCR screening and sequencing

• Expression verification:

  • Confirm expression using β-galactosidase assays if using reporter fusions

  • For direct verification of UPF0290 expression, use protein extraction protocols optimized for thermophilic proteins

By following these specialized PCR and cloning strategies, researchers can effectively manipulate the M164_1356 gene for subsequent functional studies in its native hyperthermophilic environment.