Researchers at McGill University School of Medicine have made important strides in understanding the functioning of enzymes that play an integral role in the production of antibiotics and other therapeutics. Their discoveries are published in Science.
Many of the medicines we rely on today are natural products made from earth's flora. This includes compounds made into microbes by massive enzymes called nitrosomal peptide synthetases, or NRPSs. NRPSs synthesize all kinds of antibiotics, which can kill dangerous fungi and bacteria, as well as compounds to help us fight viral infections and cancer. For example, these compounds include viomycin, an antibiotic used to treat multidrug-resistant tuberculosis; ciclosporin, widely used as an immunosuppressive in organ transplantation; and the famous antibiotic penicillin. "
Dr. Martin Jmaying, associate professor in the Department of Biochemistry at McGill and senior author of the study
In order to synthesize these drugs, NRPSs work similar to the factory assembly line, which consists of a series of workstations. Each station, called a "module," has multi-step workflows and moving parts that allow it to add one component to a growing drug building block.
Understanding the interior of the assembly line
Previous work by Dr. Jumming and others has led to a solid understanding of how a module works. Now, using a technique called X-ray crystallography in the Canadian light source in Saskatchewan and the advanced photon source in Illinois, the team was able to produce ultra-high resolution NRPS 3D images.
For the first time, they were able to make high-quality insights on how an individual module relates to a larger assembly line, by visualizing a two-modulus of NRPSs, making the antibiotic linear gramcidin (found in polysorbin treatments). . The study found a surprising lack of synchronization between modules at all points, unless they had to coordinate to cross intermediate from one workstation to another. In addition, they found that the modules were not set in a straight line or other organized fashion, but could instead be arranged in very different relative positions. "This level of massive flexibility was not expected," notes Dr. Jumming, who is also director of the McGill Center for Structural Biology. "Enzymes do gymnastics."
Since proteins are trapped in a crystal, care is taken to ensure that the results are representative of what is happening in real life. Dr. Jumming worked with his colleague, Dr. Alba Guaren, a professor at the Department of Biochemistry at McGill, to use complementary solutions data collected at the Berkeley Advanced Light Source to validate observations. "The structural community of biology is very strong at McGill. We work together to help each other collaborate, get the biophysical equipment needed for cutting-edge experiments, and train our students," said Dr. Jumming. paper, Iceenius Reimer, Max Eivanshani and Ingrid Farb are all talented McGill graduates. "The environment and his colleagues at the McGill Center for Structural Biology are important to the continued success of our labs."
Future implications for therapeutic design
The results may have implications for the production of new antibiotics and therapeutics in the long run. Since the first discovery, scientists have been excited about the possibility of bioengineering NRPS by mixing and matching workstations to produce design compounds. "Our study shows that it should be possible to mix and match these modules, but that bioengineered NRPSs must be modified at the points involved in bringing the compound from one module to another to work well, "explains Dr. Jumming. "This is something we have teamed up with Martin Weigt of Sorbonne to do as proof of the principle in labor, but that will need to be optimized for the production of designer therapeutics."
Reimer, JM, et al. (2019) Structures of dimodular unripositive peptide synthetase reveal conformational flexibility. Science. doi.org/10.1126/science.aaw4388.