In order to function properly, proteins in the body need to be perfectly arranged, or folded. Protein misfolding produces a number of problems, including diseases of aging and different cancers. A new method developed by researchers at the Texas A&M Institute of Biosciences and Technology, examines protein assembly in real time, in living cells, to find problems with assembly and diagnose the resulting diseases.1
Proteins are organic molecules made up of different combinations of 20 amino acids. For any given protein, the amino acids must join together with chemical bonds and then fold properly, in single copy as a monomer or multiple copies as an oligomer, to execute the protein’s function within cells.
Nearly a third of the proteins in the human body assemble as oligomers to perform their biological tasks. Hemoglobin, for example, assembles as a tetramer to most efficiently transport oxygen through the bloodstream. A disruption of hemoglobin’s assembly would compromise cellular uptake of oxygen, potentially causing damage to cells throughout the body due to lack of oxygen. That’s where the new study comes in.
“We developed a novel method to examine protein assembly in real time and to dissect the structure-function relations in living cells,” says Yubin Zhou, PhD, associate professor at Texas A&M and coauthor of the study. “Normally this is done in test tubes. Our study meets the urgent and critical need for quantitative assessment of protein structure and monitoring of protein actions under native conditions.”
Zhou calls the engineered, genetically-encoded mini-tags ‘MoTags,’ which is short for monomer/oligomer detection tag. The tags enable researchers to quantify the number of units in a particular protein and compare the result with the ideal number of units for that protein to identify any misfolding.
Scientists believe that protein misfolding occurs naturally during the aging process as proteins become damaged, ultimately causing some of the major diseases associated with aging, including Alzheimer’s disease, cancers, and Parkinson’s disease. A method that can quickly determine whether a protein is inappropriately assembled in real time, in living cells, will not only help scientists better understand the pathogenic mechanisms but can also aid in the diagnosis of disease and inform possible treatments.
The MoTag method can also help screen for drugs that correct the misfolding or misassembly of disease-causing or disease-associated proteins. “In addition to protein structure-function relationship studies, our approach can detect protein-to-protein, protein-to-DNA, or protein ligand-to-drug interactions,” says Guolin Ma, PhD, a postdoctoral fellow in Zhou’s lab who spearheaded the work. “Therefore, the live-cell screening assays against these interactions can be set up based on our method.”
“Our method can be widely adopted by any laboratories equipped with a standard fluorescence microscope to study protein chemistry, and thus is suitable for a broad application in the fields of protein chemistry, chemical biology, biochemistry research, as well as the development of assays to aid drug screening and therapeutic development in the near future,” says Yun (Nancy) Huang, PhD, assistant professor in the center for epigenetics and disease prevention at Texas A&M and coauthor of the study.
“Our simple methods have straightforward readouts and circumvent laborious protein expression and purification procedures,” says Huang. “We are thrilled with the broad adaptability and wide applications of MoTags in biomedical research, as well as the potential for transforming the way biochemists study their pet proteins.”
For further information, visit Texas A&M Health Science Center.
- Ma G, Zhang Q, He L, et al. Genetically encoded tags for real-time dissection of protein assembly in living cells. Chem Sci. 2018;9:5551–5555; doi: 10.1039/c8sc00839f.