Breakthrough In-Situ Cryo-EM from Zhang Lab Allows for Visualizing Atomic Details of Respiration within Native Mitochondria

May 29, 2024

The Zhang Lab developed an in-situ imaging technique to revolutionize our understanding of cellular energy production and its implications in diseases. Published in Nature, the study titled “High-resolution In-situ Structures of Mammalian Mitochondrial Respiratory Supercomplexes in Reaction within Native Mitochondria” introduces an innovative in-situ cryo-electron microscopy (cryo-EM) method. It was led by MB&B postdoctoral researcher Dr. Wan Zheng and MB&B graduate student Pengxin Chai, along with Professor Jiapeng Zhu from Nanjing University of Chinese Medicine and MB&B Assistant Professor Jack Zhang.

Mitochondrial respiratory complexes play pivotal roles in generating cellular energy and are linked to various diseases. While cryo-EM has enabled the study of these complexes, existing in-vitro methods fall short in capturing the full biological context. The author’s new technique allows for direct imaging of intact mitochondria, thus preserving their native environment. By developing a whole series of comprehensive cryo-EM image analysis approaches and computational tools, the team for the first time resolved dynamic structures of respiratory supercomplexes at unprecedented resolutions ranging from 1.8 to 2.4 Å in mitochondria.

By preserving the native membrane environment, this technique eliminates possible artifacts caused by in-vitro methods, ensuring the integrity of mitochondrial structures and allowing for the characterization of weakly assembled supercomplexes within their native membrane surroundings. Improved classification approaches revealed distinct ligand-binding states during dynamic reactions, offering insights into rapid substrate transfer and redox reactions.

Moreover, the study elucidated native lipid structures crucial for substrate transfer and redox reactions, shedding light on interactions among adjacent respiratory complexes. By also detailing protein structures embedded in intact membranes, the team highlighted the reciprocal influence between membrane geometry and supercomplex organization. Importantly, the research highlights critical differences between in-vitro and in-situ structures, emphasizing the importance of preserving the native environment for accurate characterization.

Insights gleaned from this study and future work employing this technique have the potential to transform research and treatment strategies for mitochondrial-related diseases, including cardiopathy, obesity, diabetes, neurodevelopmental disorders, neurodegenerative conditions, and various cancers. Furthermore, the methodology can be extended to study other intact organelles, opening new avenues for cellular research at the atomic level. It represents a major leap forward in our understanding of cellular energetics and holds promise for addressing numerous medical challenges in the future.

Notably, Professor Zhang began his PhD project 15 years ago by imaging whole mitochondria using cryo-electron tomography, which ended non-fruitfully due to significant technical bottlenecks at that time. “Together with my team at Yale and our collaborators, we realized this dream that traces back to 15 years ago,” said Professor Zhang. “It underscores the importance of perseverance in research and scholarship, particularly the highest level of demanding ability to master and teach the next generation of scientists a broad spectrum of knowledge across multiple major disciplines that collectively define the expansive field of modern microscopy.

According to first author Dr. Wan Zheng, Dr. Zhang’s extensive and multidisciplinary expertise in cryo-electron microscopy enabled this culmination of work to succeed. “I felt like I was learning a whole world and centuries of new, frontier knowledge across many disciplines in the Zhang lab, and I could have never, ever made this level of achievement without Professor Zhang’s dedicated mentoring.”

By: Brigitte Naughton