Recombinant Pan paniscus Cytochrome b-c1 complex subunit Rieske, mitochondrial (UQCRFS1)

What is the basic structure of Pan paniscus UQCRFS1 protein?

The UQCRFS1 protein in Pan paniscus (pygmy chimpanzee) is a Rieske domain-containing protein that functions as an essential component of the mitochondrial respiratory chain. The protein contains a characteristic Rieske-type [2Fe-2S] cluster and functions within the cytochrome bc1 complex (Complex III). The full protein sequence includes a transmembrane domain and an iron-sulfur domain responsible for electron transfer capabilities. Multiple isoforms exist with varying sequence characteristics, including X1 and X2 variants as documented in reference databases . The protein has a calculated molecular weight of approximately 29.7 kDa and consists of 274 amino acids, including a 78 amino acid N-terminal extension sequence .

How does the Rieske iron-sulfur domain contribute to electron transport in the respiratory chain?

The Rieske iron-sulfur domain in UQCRFS1 functions as a critical electron transfer component within Complex III (ubiquinol-cytochrome c reductase). This domain contains a [2Fe-2S] cluster that accepts electrons from ubiquinol and transfers them to cytochrome c1, facilitating the Q-cycle mechanism. The protein's positioning within the complex allows for dynamic interaction between the iron-sulfur domain and other subunits. Molecular dynamics simulations have revealed that rather than static interactions, the Rieske domain forms multiple dynamic hydrogen bonds and salt bridges at the cytochrome c-c1 interface . This mobility is essential for the alternating access mechanism whereby the Rieske domain moves between positions to facilitate electron transfer from ubiquinol at the Qo site to cytochrome c1, driving proton translocation across the inner mitochondrial membrane and contributing to the proton-motive force necessary for ATP synthesis .

What are the key differences between UQCRFS1 and other Rieske-domain containing proteins?

UQCRFS1 is specifically a component of the respiratory complex III, distinguishing it from other Rieske domain-containing proteins that function in different biological contexts. While the core [2Fe-2S] cluster structure is conserved across Rieske proteins, UQCRFS1 contains specific structural features that enable its function in the respiratory chain:

• Transmembrane anchoring domain (UCR_TM) that integrates the protein into the inner mitochondrial membrane

• Specific interface residues that facilitate interaction with cytochrome c1

• N-terminal extension sequence (78 amino acids) that differs from Rieske domains in oxygenases

Unlike Rieske oxygenases, which use their [2Fe-2S] cluster in conjunction with a mononuclear iron center to catalyze oxidation reactions on various substrates , UQCRFS1 functions purely in electron transport without direct substrate oxidation. Furthermore, UQCRFS1 operates within a multi-subunit complex (Complex III), whereas many Rieske oxygenases function as part of different enzyme architectures with distinct catalytic outcomes .

What are the recommended protocols for expression and purification of recombinant Pan paniscus UQCRFS1?

Expression and purification of recombinant Pan paniscus UQCRFS1 requires careful consideration of the protein's structural properties and cofactor requirements. Based on successful approaches with related proteins:

Expression System Selection:

• E. coli-based expression systems should include iron supplementation and co-expression of iron-sulfur cluster assembly proteins

• Mammalian expression systems (particularly HEK293 or CHO cells) may provide better post-translational modifications

• Baculovirus-insect cell systems have shown success for complex mitochondrial proteins

Purification Strategy:

• Utilize affinity chromatography with His-tag or combined His/MBP-tag systems similar to those employed for related Rieske proteins

• Include detergent solubilization step when working with the full-length protein (typically n-dodecyl-β-D-maltoside)

• Incorporate anaerobic handling procedures to prevent oxidative damage to the [2Fe-2S] cluster

• Apply size exclusion chromatography as a final purification step

Quality Control Methods:

• UV-visible spectroscopy to confirm characteristic absorption peaks of the [2Fe-2S] cluster

• Western blot verification using antibodies like those described in search result

• Activity assays measuring electron transfer capability

Storage in buffer containing 50% glycerol with Tris base at -20°C is appropriate for short-term storage, while -80°C is recommended for extended storage periods to maintain protein integrity .

How can researchers effectively validate antibody specificity for Pan paniscus UQCRFS1 in various experimental applications?

Validating antibody specificity for Pan paniscus UQCRFS1 requires a multi-faceted approach:

Recommended Validation Techniques:

• Western Blot Validation:

  • Use positive controls from tissues with high mitochondrial content (heart tissue from various species shows cross-reactivity with antibodies like 18443-1-AP)

  • Observe expected molecular weight (approximately 25 kDa observed vs. 30 kDa calculated)

  • Include UQCRFS1 knockout/knockdown samples as negative controls

• Immunoprecipitation Validation:

  • Perform IP using 0.5-4.0 μg antibody for 1.0-3.0 mg of total protein lysate

  • Confirm pulled-down protein identity by mass spectrometry

  • Assess non-specific binding through reverse IP experiments

• Immunohistochemistry Specificity:

  • Apply recommended dilution (1:250-1:1000) with appropriate antigen retrieval (TE buffer pH 9.0 or citrate buffer pH 6.0)

  • Include tissue panels with varying UQCRFS1 expression levels

  • Perform peptide competition assays to confirm epitope specificity

• Cross-Species Reactivity Assessment:

  • Test antibody against recombinant UQCRFS1 from different species

  • Align epitope regions across species to predict cross-reactivity

Optimization Guidelines:

• Titrate antibody concentrations in each application to determine optimal signal-to-noise ratio

• Sample-dependent optimization may be necessary, particularly for tissues with varying mitochondrial content

What advanced analytical techniques are most informative for studying the [2Fe-2S] cluster properties in UQCRFS1?

Several sophisticated analytical techniques are essential for comprehensive characterization of the [2Fe-2S] cluster in UQCRFS1:

Spectroscopic Methods:

• Electron Paramagnetic Resonance (EPR) Spectroscopy:

  • Can distinguish between oxidized and reduced states of the [2Fe-2S] cluster

  • Temperature-dependent measurements reveal electronic properties specific to Rieske-type clusters

  • Provides information on cluster integrity and redox properties

• Mössbauer Spectroscopy:

  • Using 57Fe-enriched samples to characterize iron oxidation states

  • Distinguishes the unique Fe2+/Fe3+ pair in Rieske clusters from other iron-sulfur configurations

  • Allows monitoring of redox transitions during functional studies

• X-ray Absorption Spectroscopy (XAS):

  • X-ray absorption near-edge structure (XANES) analysis reveals oxidation state

  • Extended X-ray absorption fine structure (EXAFS) provides detailed geometric information

  • Can be performed on frozen solutions without crystallization requirement

Electrochemical Methods:

• Protein film voltammetry to determine redox potentials

• Spectroelectrochemistry combining UV-visible spectroscopy with controlled redox potential

Structural Techniques:

• Hydrogen-deuterium exchange mass spectrometry (HDX-MS) to study dynamic conformational changes

• Cryo-electron microscopy for structural analysis within the intact complex

• Molecular dynamics simulations to study the dynamic behavior of the Rieske domain, particularly valuable for understanding the mobile nature of interactions at the cytochrome c-c1 interface

What evolutionary insights can be gained from studying Pan paniscus UQCRFS1 compared to other primates and mammals?

The evolutionary study of UQCRFS1 across species provides valuable insights into mitochondrial respiratory complex development:

Comparative Analysis Framework:

• Sequence conservation analysis between Pan paniscus UQCRFS1 and orthologs from humans, other great apes, and more distant primates

• Examination of selection pressures on functional domains versus variable regions

• Correlation of sequence variations with species-specific metabolic adaptations

Evolutionary Significance:

• The Rieske protein represents an interesting case study in the evolution of the mitochondrial respiratory chain, as it was once encoded in the mitochondrial genome but migrated to the nuclear genome in most eukaryotes

• Experimental evidence from yeast studies demonstrates that the gene can be artificially relocated back to mitochondria while maintaining functionality, providing insights into evolutionary gene transfer events

• Comparative analyses can reveal adaptations related to energy metabolism differences across primate lineages

Research Applications:

• Phylogenetic analyses using UQCRFS1 sequence data from multiple species

• Molecular clock studies to estimate divergence times between species

• Investigation of positive selection signatures in metabolically specialized lineages

How can the Rieske domain be engineered to modify its electron transfer properties or substrate interactions?

Engineering the Rieske domain for modified properties requires strategic approaches based on structure-function relationships:

Engineering Strategies:

• Redox Potential Modification:

  • Target the conserved cysteine and histidine residues coordinating the [2Fe-2S] cluster

  • Manipulate the electrostatic environment surrounding the cluster by altering charged residues

  • Introduce hydrogen bonding networks that stabilize specific redox states

• Interface Engineering:

  • Modify residues involved in protein-protein interactions at the cytochrome c-c1 interface

  • Target the dynamic hydrogen bonds and salt bridges identified in molecular dynamics simulations

  • Rational design based on comparative analysis of interface residues across species

• Substrate Channel Modification:

  • Apply lessons from Rieske oxygenase engineering where "hotspot" regions control substrate interactions

  • Target specific structural elements that guide substrate access or product release

Experimental Approaches:

• Site-directed mutagenesis of specific residues identified through structural analysis

• Domain swapping between Rieske domains from different functional contexts

• Directed evolution with appropriate selection systems

• Computational design followed by experimental validation

Researchers should note that insights from the engineering of Rieske oxygenases, where structural blueprints have been used to rationally engineer substrate selectivity and reaction specificity, may provide valuable principles applicable to UQCRFS1 engineering .

What insights can be gained from the successful relocation of the RIP1 gene from nucleus to mitochondria in yeast models?

The successful relocation of the RIP1 gene (yeast homolog of UQCRFS1) from the nucleus to mitochondria provides several profound insights:

Experimental Findings:
Biolistic transformation was used to relocate the nuclear RIP1 gene into mitochondria in Saccharomyces cerevisiae. The mitochondrial copy (RIP1m) was integrated between the cox1 and atp8 genes using the S. cerevisiae cox1 promoter and terminator regions. This mitochondrially-encoded RIP1m was:

• Mitotically stable

• Successfully expressed

• Able to complement a deletion of the nuclear gene

• Capable of producing functional Rip1 protein, albeit at lower levels than wild-type

• Sufficient to maintain a functional cytochrome bc1 complex and respiratory competence

Implications for Understanding Evolutionary Gene Transfer:

• Demonstrates the plasticity of gene expression systems across cellular compartments

• Provides experimental evidence supporting theories about the evolutionary migration of genes from mitochondria to the nucleus

• Suggests that reverse gene transfer (nucleus to mitochondria) is functionally possible, despite being rare in natural evolution

• Offers a model system for studying the requirements for functional gene expression in different cellular compartments

Applications for Biotechnology and Basic Research:

• Development of new tools for mitochondrial genome engineering

• Approaches for manipulating respiratory chain components for research purposes

• Potential therapeutic strategies for mitochondrial disorders through gene relocation

• Experimental platform for studying factors affecting gene expression efficiency in mitochondria

This work represents an "artificial reversal of evolutionary events" and provides a unique experimental system for studying the evolutionary dynamics of gene transfer between organelles and the nucleus .

How can recombinant Pan paniscus UQCRFS1 be utilized in comparative studies of respiratory complex assembly and function?

Recombinant Pan paniscus UQCRFS1 offers valuable opportunities for comparative studies:

Experimental Applications:

• Interspecies Complex III Reconstitution:

  • Integration of Pan paniscus UQCRFS1 with complex III components from other species

  • Analysis of assembly efficiency, stability, and functional parameters

  • Identification of species-specific compatibility factors

• Chimeric Protein Analysis:

  • Creation of chimeric UQCRFS1 proteins containing domains from different species

  • Identification of critical regions determining species-specific functions

  • Assessment of evolutionary constraints on domain interactions

• Functional Complementation Studies:

  • Testing ability of Pan paniscus UQCRFS1 to rescue UQCRFS1-deficient systems from various species

  • Quantitative assessment of functional parameters (electron transfer rates, complex stability)

  • Correlation of sequence differences with functional outcomes

Methodological Approaches:

• In vitro reconstitution of complex III with purified components

• Cell-based assays using UQCRFS1-knockout backgrounds

• Biophysical characterization of isolated complexes using spectroscopic and structural methods

• Respirometry analyses to assess functional outcomes

Data Collection Framework:

• Standardized protocols for expression and purification to enable direct comparisons

• Integration of functional, structural, and evolutionary data

• Development of comprehensive databases documenting interspecies variations

What are the most significant challenges in expressing and characterizing active recombinant Rieske proteins, and how can they be addressed?

Expression and characterization of active recombinant Rieske proteins present several significant challenges:

Major Challenges and Solutions:

• Iron-Sulfur Cluster Assembly:
  Challenge: Ensuring proper [2Fe-2S] cluster formation during heterologous expression
  Solutions:

  • Co-expression with iron-sulfur cluster assembly proteins (ISC or SUF system components)

  • Supplementation with iron and sulfur sources during expression

  • Expression under microaerobic conditions to prevent cluster oxidation

  • Use of specialized E. coli strains with enhanced Fe-S cluster assembly capabilities

• Membrane Integration:
  Challenge: UQCRFS1 contains a transmembrane domain requiring proper membrane insertion
  Solutions:

  • Expression as truncated soluble domain for some applications

  • Utilization of membrane-mimetic systems (nanodiscs, liposomes) for full-length protein

  • Application of specialized membrane protein expression systems

  • Detergent screening for optimal solubilization conditions

• Functional Validation:
  Challenge: Confirming electron transfer functionality in isolated context
  Solutions:

  • Development of reconstituted electron transfer systems

  • Coupling with artificial electron donors/acceptors

  • Spectroelectrochemical characterization

  • Integration into minimal reconstituted respiratory complexes

• Structural Characterization:
  Challenge: Obtaining structural information on the dynamic Rieske domain
  Solutions:

  • Application of complementary structural techniques (X-ray crystallography, cryo-EM, NMR)

  • Use of molecular dynamics simulations to model dynamic behavior

  • Strategic introduction of probes or labels for tracking conformational changes

  • Hydrogen-deuterium exchange mass spectrometry for conformational dynamics

How might insights from Rieske oxygenase engineering be leveraged for studying or modifying UQCRFS1 function?

Although Rieske oxygenases and UQCRFS1 have distinct functions, engineering principles from Rieske oxygenases can be adapted for UQCRFS1 research:

Transferable Engineering Principles:

• Structural Hotspot Identification:
  Rieske oxygenase research has identified specific "hotspot" regions that can be targeted to alter catalytic outcomes . Similar approaches could identify critical regions in UQCRFS1 that influence:

  • Redox potential of the [2Fe-2S] cluster

  • Conformational dynamics during electron transfer

  • Interaction with other complex III components

• Predictive Tuning Strategies:
  Research has demonstrated that Rieske oxygenases can be predictively tuned to catalyze divergent reactions . For UQCRFS1, similar approaches might enable:

  • Adjustment of electron transfer rates

  • Alteration of sensitivity to inhibitors

  • Enhancement of stability under various conditions

• Domain Engineering Approaches:
  Leveraging insights from the successful engineering of Rieske monooxygenase TsaM , researchers could:

  • Apply targeted mutagenesis of specific UQCRFS1 residues predicted to influence function

  • Create chimeric constructs combining domains from different Rieske proteins

  • Implement directed evolution with appropriate selection systems

Methodological Framework:

• Structural analysis to identify potential engineering targets

• Computational prediction of functional effects

• Targeted mutagenesis based on insights from Rieske oxygenase engineering

• Functional characterization focusing on electron transfer properties

• Iterative optimization based on functional outcomes

These approaches could generate valuable research tools for understanding respiratory complex function and potentially contribute to the development of novel therapeutic strategies for mitochondrial disorders involving Complex III dysfunction.

Key Isoforms of Pan paniscus UQCRFS1

Data compiled from GenScript database information

Recommended Antibody Applications for UQCRFS1 Detection

Based on data from Proteintech antibody 18443-1-AP

Comparison of Key Structural Features Between Rieske Proteins

Compiled from information in references