Recent research spearheaded by a team of scientists, Zhou Hong, Liu Shengtang, Yin Xiuhua, Li Zengpeng, Yang Zaixing, and Zhou Ruhong, has made a significant leap in the field of antibody engineering. Published on June 26, 2020, in the Biophysical Journal, the study titled “Molecular Origin of the Stability Difference in Four Shark IgNAR Constant Domains” addresses a critical aspect of biotechnology: the stability of antibodies. The work painstakingly deconstructs the molecular reasons behind the stability variance in shark immunoglobulin new antigen receptors constant domains (C1-C4). The findings of this research not only contribute to the fundamental understanding of immune system evolution but also provide essential insights that could revolutionize the design of stable therapeutic antibodies.
Intriguing IgNARs: Sharks Shedding Light on Antibody Design
Antibody stability is a cornerstone for the effectiveness of many therapeutic applications. The reliable performance of antibodies in diagnostic and therapeutic procedures depends heavily on their structural integrity over time. Recognizing this, the collaborative international research team plunged into the biological depths inhabited by cartilaginous fish, such as sharks, to extract clues for enhancing antibody stability.
Sharks are remarkable in that their immune system has fashioned IgNAR (immunoglobulin new antigen receptor) antibodies, which stand apart in terms of stability and resilience. Understanding the mechanisms behind IgNARs’ stability offers a blueprint for advancing human antibody therapeutics with potentially longer shelf lives and reduced manufacturing costs. For biotechnological applications, the implications are nothing short of transformative.
A Molecular Dynamics Odyssey
The study in question utilized cutting-edge molecular dynamics simulations to explore the stability of four shark IgNAR constant domains. These simulations provided an unprecedented view of the unfolding pathways and conformational energy landscapes, especially in challenging conditions mimicking those that may lead to antibody denaturation, such as the presence of 8 M urea at 380 K.
The researchers’ simulations revealed a hierarchy of stability among the four IgNAR domains, with C2 emerging as the most resilient. Experimental evidence corroborated this conclusion, validating the predictive power of the molecular simulations. The C1 and C3 domains demonstrated a similar pattern of unfolding, initiating at the edge strands, particularly strand g, moving inward. Meanwhile, the C2 domain displayed a distinct, highly stable ‘sandwich-like’ configuration thanks to a trio of salt bridges (R339-E322-R341).
To further test the impact of these salt bridges on stability, the researchers designed mutations that disrupted these specific interactions. The results of these mutations confirmed that the salt bridges are instrumental in conferring stability to the IgNAR domains. In the C4 domain, another salt bridge, D80-K104, contributed to its stability but in a less prominent manner.
Beyond the Salt Bridges: Hydrophobicity and Stability
The saga of IgNAR stability does not end with salt bridges. The study also indicated a positive correlation between the hydrophobicity score of the domains’ cores and their stability. This relationship suggests that evolution has possibly fine-tuned these domains by optimizing the balance between hydrophilic and hydrophobic interactions.
Implications for Antibody Engineering
Armed with this molecular understanding, scientists can now contemplate designing human antibodies inspired by the inherent stability of shark IgNARs. The research team’s discovery of the ‘salt-bridge cluster’ strategy in particular holds great promise for designing therapeutics that are robust against denaturation.
References
The DOI for the original research is 10.1016/j.bpj.2019.04.013, marking it as a significant contribution to the field of biophysical research. For further reading, one may consult the following references, which provide context and additional insights into immune system evolution, molecular dynamics simulations, and antibody engineering:
1. Dooley, H., and M. F. Flajnik. 2006. “Antibody repertoire development in cartilaginous fish.” Dev. Comp. Immunol. 30:43-56.
2. Litman, G. W., M. K. Anderson, and J. P. Rast. 1999. “Evolution of antigen-binding receptors.” Annu. Rev. Immunol. 17:109-147.
3. Flajnik, M. F. 2002. “Comparative analyses of immunoglobulin genes: surprises and portents.” Nat. Rev. Immunol. 2:688-698.
4. Criscitiello, M. F. 2014. “What the shark immune system can and cannot provide for the expanding design landscape of immunotherapy.” Expert Opin. Drug Discov. 9:725-739.
5. Kovaleva, M., L. Ferguson, and C. Barelle. 2014. “Shark variable new antigen receptor biologics – a novel technology platform for therapeutic drug development.” Expert Opin. Biol. Ther. 14:1527-1539.
Keywords
1. Antibody stability
2. Shark IgNAR domains
3. Molecular dynamics simulations
4. Antibody engineering
5. Biotechnology