Molecular Research Sheds Light on Disease

Posted on Tuesday, February 9th, 2021

Close up image of proteins, purple in colour.
There are about 100,000 types of proteins in the human body, responsible for a range of essential tasks including growth, healing, and protecting against disease.

Examining working mechanisms of protein machineries in our body could inform future studies of disease.

The human body is a complex machine, and proteins are the molecular engines. Proteins are a category of biological macromolecules that perform many functions in the body. Protein homeostasis, a network that maintains proteins in the correct concentrations and configurations, ensures protein function and cell health. Protein homeostasis is maintained by a large network of molecular machineries, which are involved in protein synthesis, folding, unfolding and degradation. When mutations occur, protein homeostasis can be disrupted, and diseases, such as Alzheimer’s or and Parkinson’s, may arise. Understanding how protein homeostasis is maintained is critical to identify how and why some diseases occur.

Protein Machines

University of Guelph Chemistry professor Dr. Rui Huang is investigating an important protein machine called p97, a versatile enzyme that participates in several cellular functions in humans. Mutations to p97 can lead to diseases that affect muscle, bone and the brain. Huang and collaborators assessed the structure and dynamics of p97 and its disease-related mutants. They determined how complex formation between p97 and its partners as well as the cooperativity within p97 itself affected its cellular function.

State-of-the-art Techniques

The researchers applied “nuclear magnetic resonance (NMR) spectroscopy” and “single-particle cryo-electron microscopy (cryo-EM).” With NMR spectroscopy, proteins are labelled with specific isotopes, providing structural and dynamic information at the atomic level. In cryo-EM, protein particles are flash frozen and trapped in a thin film of ice, enabling researchers to view the protein’s structure at the time of freezing. Using an advanced algorithm, the team observed 14 unique arrangements of a mutant form of p97 and determined the populations of all conformers.

Image showing p97 mutant under a cryo-electron microscope

Figure from the article: 14 unique conformations of a p97 mutant observed by cryo-electron microscopy. 

The Big Picture

Although the study found that there was no cooperation in the conformational change (positional arrangement) of a certain domain between neighbours in this p97 mutant, these results are due to the composition of the p97 subunits under study: each unit carried the disease mutation. However, many real patients carry just one copy of the mutation alongside a non-mutated gene. A previous study by Huang and collaborators showed that there is a high level of cooperation between neighbours in a p97 complex with heterogeneous subunit composition. 

“There are synergies between data gleaned from cryo-electron microscopy and Nuclear Magnetic Resonance spectroscopy,” explains Huang. “By considering results born out of both techniques, we have shown that the protein composition impacts whether or not cooperation occurs between neighbours. These insights will inform studies of disease.”

Dr. Rui Huang headshot

Rui Huang is an Assistant Professor in the Department of Chemistry.

This work was supported by the Canadian Institutes of Health Research grants FDN-503573 and PJT-162186.

Huang R, Ripstein ZA, Rubinstein JL, Kay LE. Probing Cooperativity of N‐Terminal Domain Orientations in the p97 Molecular Machine: Synergy Between NMR Spectroscopy and Cryo‐EM. Angew Chem Int Ed. 2020 Dec 7. doi: 10.1002/anie.202009767

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