Cellular defense against oxidative stress

Unlock Cellular Defense: How Ino-1 Protects Against Oxidative Stress

Author's portrait.
Lena Kashyap in Science & Nature August 2025 • 4 min read.

"Discover the critical role of Myo-inositol-1-phosphate synthase in Corynebacterium glutamicum's survival under stress"


In the ever-changing world of aerobic existence, organisms constantly face the challenge of oxidative stress. This stress, resulting from an imbalance between the production and clearance of reactive oxygen species (ROS), can wreak havoc on crucial macromolecules like proteins, lipids, and DNA. To combat this, organisms employ various protective mechanisms to maintain cellular health.

One such mechanism involves low-molecular-weight (LMW) thiols, which act as redox buffers to defend against ROS and modify proteins, preserving the cytoplasm's reduced state. While eukaryotes and gram-negative bacteria utilize glutathione (GSH) for this purpose, certain gram-positive bacteria, including Corynebacterium, Mycobacterium, Rhodococcus, and Streptomyces, rely on mycothiol (MSH) as their functional equivalent.

Myo-inositol-1-phosphate synthase (Ino-1) plays a pivotal role in generating MSH by synthesizing myo-inositol-phosphate, a crucial precursor substrate. Although Ino-1's functions have been extensively studied in eukaryotes, its physiological and biochemical roles in bacteria remain largely unexplored. Recent studies now highlight Ino-1's potential significance in stress resistance, prompting a deeper investigation into its protective mechanisms.

How Does Ino-1 Function as a Cellular Shield?

Cellular defense against oxidative stress

To investigate Ino-1's protective functions, researchers conducted a detailed study focusing on Corynebacterium glutamicum. By removing the ino-1 gene, they observed significant consequences, including reduced cell viability, increased ROS production, and elevated protein carbonylation levels under various stress conditions. These findings strongly suggest that Ino-1 is essential for oxidative stress resistance.

The absence of MSH in the Δino-1 mutant further corroborated these observations, underscoring Ino-1's role in maintaining MSH levels. To confirm Ino-1's functionality, homologous expression in C. glutamicum yielded an active protein. However, when expressed in Escherichia coli BL21(DE3), it lacked measurable activity, indicating that proper folding is crucial for its enzymatic function.

Here are the key findings:
  • Deletion Impact: Removing the ino-1 gene significantly impaired the cell's ability to withstand oxidative stress.
  • ROS Levels: The mutant strain showed increased ROS production, indicating a compromised defense against oxidative damage.
  • Protein Carbonylation: Elevated protein carbonylation confirmed that proteins were more susceptible to oxidative damage in the absence of Ino-1.
  • MSH Deficiency: The absence of MSH in the mutant highlighted Ino-1's role in its synthesis.
  • Expression Matters: While Ino-1 was functional when expressed in its native host, C. glutamicum, it was inactive in E. coli BL21(DE3), suggesting folding issues.
Further analyses indicated that Ino-1 expressed in E. coli BL21(DE3) was not folded into a catalytically competent conformation, explaining its lack of activity. Collectively, these results unequivocally demonstrate Ino-1's critical role in mediating oxidative resistance in C. glutamicum.

The Future of Ino-1 Research

This research illuminates the versatile protective roles of Ino-1 in C. glutamicum, offering a promising strategy to engineer more robust industrial strains. By understanding and harnessing Ino-1’s capabilities, scientists can develop novel approaches to enhance cellular defense mechanisms, paving the way for advancements in biotechnology and industrial applications. Further studies may explore how to optimize Ino-1 expression and function to maximize its protective effects under diverse stress conditions.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

1

What is the primary function of Ino-1 in Corynebacterium glutamicum?

In Corynebacterium glutamicum, Ino-1, or Myo-inositol-1-phosphate synthase, is vital for producing myo-inositol-phosphate, a precursor to mycothiol (MSH). MSH then acts as a major antioxidant, protecting the cell from oxidative stress by neutralizing reactive oxygen species (ROS). Ino-1's activity directly influences the cell's ability to withstand oxidative damage.

2

Why is mycothiol (MSH) important for certain bacteria like Corynebacterium glutamicum?

Mycothiol (MSH) serves as the functional equivalent of glutathione (GSH) in certain gram-positive bacteria, including Corynebacterium glutamicum. It functions as a low-molecular-weight (LMW) thiol, acting as a redox buffer to protect against reactive oxygen species (ROS) and to modify proteins, preserving the reduced state of the cytoplasm. This is particularly crucial for these bacteria because, unlike eukaryotes and gram-negative bacteria that use GSH, they depend on MSH for their antioxidant defense.

3

What happens when the ino-1 gene is removed from Corynebacterium glutamicum?

When the ino-1 gene is removed from Corynebacterium glutamicum, the resulting mutant strain exhibits several detrimental effects. Researchers observed reduced cell viability, increased production of reactive oxygen species (ROS), and elevated protein carbonylation levels. These changes indicate that the absence of Ino-1 impairs the cell's ability to cope with oxidative stress. Furthermore, the mutant strain lacks mycothiol (MSH), confirming Ino-1's critical role in MSH synthesis.

4

Why does Ino-1 function properly in Corynebacterium glutamicum but not in Escherichia coli BL21(DE3)?

Ino-1 is functional when expressed in its native host, Corynebacterium glutamicum, because it can fold into a catalytically competent conformation. However, when Ino-1 is expressed in Escherichia coli BL21(DE3), it lacks measurable activity because it does not fold correctly. Proper folding is essential for Ino-1 to perform its enzymatic function. This suggests that specific chaperones or environmental conditions present in C. glutamicum, but not in E. coli, are necessary for Ino-1 to achieve its active, functional form.

5

What are the potential future applications of understanding Ino-1's role in cellular defense?

Understanding Ino-1's role in cellular defense presents several promising future applications, particularly in biotechnology and industrial sectors. By harnessing Ino-1’s protective capabilities, scientists can engineer more robust industrial strains of Corynebacterium glutamicum or other bacteria. Optimizing Ino-1 expression could enhance cellular defense mechanisms under diverse stress conditions, improving the efficiency and resilience of biotechnological processes. This research may also lead to the development of novel strategies for enhancing cellular robustness in various other organisms and applications.

Newsletter Subscribe

Subscribe to get the latest articles and insights directly in your inbox.