Recombinant Carassius auratus Cytochrome c oxidase subunit 2 (mt-co2)

What expression systems are commonly used for recombinant Carassius auratus MT-CO2 production?

E. coli remains the predominant expression system for MT-CO2 protein production due to its efficiency and cost-effectiveness. The methodological approach includes:

• Gene cloning: Amplify the full-length cDNA of MT-CO2 from Carassius auratus tissue samples

• Vector selection: Subclone into expression vectors such as pET-32a that contain:

  • Inducible promoter (T7)

  • Affinity tag sequences (6×His-tag)

  • Antibiotic resistance markers

• Host strain: Transform into specialized E. coli strains such as Transetta (DE3)

• Induction: Express using isopropyl β-d-thiogalactopyranoside (IPTG)

• Purification: Use affinity chromatography with Ni(2+)-NTA agarose for His-tagged proteins

The recombinant protein typically appears at approximately 44 kDa on SDS-PAGE when expressed with fusion tags . Expression yields of approximately 50 μg/mL of fusion protein have been reported .

How can researchers assess the purity and functionality of recombinant MT-CO2?

A multi-step approach is recommended for comprehensive assessment:

Purity assessment:

• SDS-PAGE analysis (target: >90% purity)

• Western blotting using anti-MT-CO2 antibodies to confirm identity and molecular weight

Functionality assessment:

• UV-spectrophotometer analysis to measure the protein's ability to catalyze oxidation of substrate Cytochrome C

• Infrared spectrometer analysis to characterize protein structure and function

• Enzymatic activity assays measuring electron transfer rates

A typical validation workflow includes:

• Run purified protein on 10-12% SDS-PAGE alongside molecular weight markers

• Transfer to PVDF membrane and probe with specific antibodies

• Measure enzyme kinetics by monitoring cytochrome c oxidation at 550 nm

• Compare activity parameters (Km, Vmax) with published values for similar proteins

What are the optimal storage conditions for recombinant Carassius auratus MT-CO2?

Based on established protocols for similar mitochondrial proteins :

Important considerations:

• Repeated freeze-thaw cycles significantly reduce activity and should be strictly avoided

• For sensitive applications, adding protease inhibitors is recommended

• Stability studies show activity retention of >85% after 6 months when stored properly

How does C. auratus MT-CO2 sequence and structure compare with other species in evolutionary studies?

MT-CO2 serves as an excellent marker for evolutionary studies due to its conserved function across species. Comparative analysis methodology typically includes:

• DNA extraction from various Carassius species and related taxa

• PCR amplification using conserved primers targeting the MT-CO2 gene

• Sequencing of amplified products

• Multiple sequence alignment using software like Clustal W

• Phylogenetic analysis using distance-based methods such as Neighbor-Joining

Studies have revealed significant findings:

• Within the Carassius genus, MT-CO2 sequences show high conservation but with distinct haplotype variations between populations

• Comparison between C. auratus and C. cuvieri shows approximately 95% sequence identity in mitochondrial genes, suggesting recent divergence

• Haplotype diversity analysis can distinguish between geographically isolated populations of the same species

Researchers have identified distinct MT-CO2 haplotypes within C. auratus populations, including C01B (general haplotype, 83.33%), C02B (8.33%), and C10B (8.33%) , indicating population-specific genetic markers that can be used for conservation and evolutionary studies.

What experimental approaches can be used to study MT-CO2 activity in goldfish under hypoxic conditions?

Goldfish possess remarkable adaptability to hypoxia, making them excellent models for studying respiratory adaptation. A comprehensive experimental approach includes:

Experimental design:

• Acclimation phase: Maintain goldfish in normoxic conditions (dissolved O₂ >7 mg/L) for baseline measurements

• Hypoxia exposure: Gradually reduce oxygen levels to create mild (4-5 mg/L), moderate (2-3 mg/L), or severe (<1 mg/L) hypoxia

• Tissue sampling: Extract tissues at designated time points (0h, 6h, 24h, 72h, 1 week)

• Mitochondrial isolation: Extract intact mitochondria using differential centrifugation

Analytical methods:

• Enzyme activity: Measure cytochrome c oxidase activity spectrophotometrically by monitoring the oxidation of reduced cytochrome c at 550 nm

• Expression analysis: Quantify MT-CO2 mRNA and protein levels using qPCR and western blotting

• Respirometry: Measure mitochondrial oxygen consumption using high-resolution respirometry

• Blue native PAGE: Assess respiratory supercomplex assembly under hypoxic conditions

Research has shown that goldfish can maintain or even improve cardiac performance under hypoxic conditions , suggesting specialized adaptations in MT-CO2 and the respiratory chain. The heart of C. auratus demonstrates extraordinary biochemical-metabolic plasticity and adaptive potential under low oxygen conditions .

How does elevated CO₂ affect MT-CO2 expression and function in goldfish?

Rising atmospheric CO₂ levels present a significant environmental challenge for aquatic organisms. Methodologies to study MT-CO2 under elevated CO₂ include:

Experimental setup:

• Use open-top chambers flushed with ambient (400±10μL/L) or elevated (600±10μL/L) CO₂

• Maintain water-sediment ecosystem to mimic natural conditions

• Monitor pH values continuously, as CO₂ elevation reduces water pH

Effect measurements:

• Tissue-specific expression: Extract RNA/protein from various tissues (gill, liver, brain, muscle) to quantify MT-CO2 levels

• Enzyme kinetics: Compare cytochrome c oxidase activity under normal vs. elevated CO₂

• ROS production: Measure reactive oxygen species generation in isolated mitochondria

• Metabolic rate: Monitor oxygen consumption patterns using respirometry

Research findings indicate that elevated CO₂ (600±10μL/L) causes:

• Increased oxidative stress in fish tissues

• Higher ROS intensity in liver and brain

• Altered metabolic responses that may affect mitochondrial function

• Changes in antioxidant defenses (lower GSH content)

These physiological responses suggest that MT-CO2 function may be modulated as part of the adaptive response to elevated CO₂, potentially through post-translational modifications or changes in expression patterns.

What role does MT-CO2 play in the remarkable cardiac adaptability of goldfish to environmental stressors?

Goldfish hearts demonstrate exceptional adaptability to environmental challenges, particularly hypoxia. MT-CO2, as a critical component of the respiratory chain, contributes to this adaptation through:

Cardiac performance mechanisms:

• Unlike mammals, goldfish can maintain or even improve cardiac function under hypoxia

• The heart of C. auratus functions as a typical volume pump with cardiac output values of approximately 11.85 mL/min/kg at 18°C

• Cardiac adaptability involves complex shifts in mitochondrial function

Research approaches:

• In vitro working heart preparations: Measure cardiac parameters under controlled conditions

• Mitochondrial respiration analysis: Compare respiratory capacities between normoxic and hypoxic hearts

• Supercomplex profiling: Assess changes in respiratory chain organization

• Proteomics: Identify post-translational modifications of MT-CO2 during adaptation

Studies have revealed that goldfish hearts show remarkable sensitivity to filling pressure changes and possess specialized mechanisms for maintaining ATP production during oxygen limitation, potentially involving modified MT-CO2 function or expression patterns.

The Frank-Starling response is particularly robust in teleost fish like goldfish , and research suggests that nitric oxide (NO) modulation of cardiac function may interact with respiratory chain components including MT-CO2 .

How can molecular docking and site-directed mutagenesis be used to study functional domains of Carassius auratus MT-CO2?

Molecular docking and site-directed mutagenesis offer powerful approaches to understand structure-function relationships in MT-CO2:

Molecular docking methodology:

• Generate three-dimensional model of MT-CO2 using homology modeling or structural determination

• Identify potential binding pockets using computational tools

• Dock substrate molecules or inhibitors in silico

• Analyze binding energies and interaction patterns

For example, researchers have used molecular docking to identify that allyl isothiocyanate (AITC) can form a 2.9 Å hydrogen bond with Leu-31 in MT-CO2 , providing insight into potential regulatory mechanisms.

Site-directed mutagenesis approach:

• Target selection: Based on sequence conservation and docking results, identify critical residues:

  • Cysteine residues at positions 196 and 200 (CuA center)

  • Conserved histidine at position 204

  • Residues identified through molecular docking (e.g., Leu-31)

• Experimental workflow:

  • Design mutagenic primers for PCR-based mutagenesis

  • Generate mutant constructs in expression vectors

  • Express and purify mutant proteins

  • Compare activity with wild-type using spectroscopic and kinetic assays

This combined approach allows researchers to validate in silico predictions with experimental data, providing deeper understanding of MT-CO2 function at the molecular level.