Probing Proteins: Leveraging Microgravity for Medically Important Molecular Crystallization
NASA astronaut Serena Auñón-Chancellor mixes protein crystal samples onboard the ISS. BioServe Protein Crystallography-1 seeks to demonstrate the feasibility of conducting protein crystal growth in real time onboard the space station. Crew members add solutions to the hardware, observe the crystals that form, and adjust for follow-on experiments.
Media Credit: NASA
August 7, 2019 • By Amelia Williamson Smith, Staff Writer
To advance research on important health issues facing people on Earth, researchers are taking protein crystallization up to space—where crystals often grow larger and with higher order than on the ground. Three investigations recently launched on SpaceX’s 18th commercial resupply services (CRS) mission seek to leverage the International Space Station (ISSInternational Space Station) U.S. National Laboratory to improve the crystallization of several medically important proteins.
Comparison of space-grown (left) and Earth-grown (right) protein crystals
Media Credit: NASANational Aeronautics and Space Administration
An investigation from the University of Toledo is crystallizing a protein involved in Salmonella contamination, a protein related to heart attack and liver disease, and a complex of two proteins involved in DNA repair. Another investigation from Dover Lifesciences is crystallizing large protein complexes that could aid in the development of drugs to treat metabolic diseases and possibly cancer. A third investigation from MicroQuin could enable the company to enhance its breast cancer therapeutic and create a pipeline of new drugs to treat other types of cancer.
Proteins play a crucial role in human health, and knowing the structure of proteins involved in certain health conditions can help scientists develop new ways to prevent and treat disease. To figure out a protein’s structure, scientists crystallize the protein and use methods such as X-ray diffraction or neutron diffraction to determine the placement of atoms within the crystal.
In the microgravityThe condition of perceived weightlessness created when an object is in free fall, for example when an object is in orbital motion. Microgravity alters many observable phenomena within the physical and life sciences, allowing scientists to study things in ways not possible on Earth. The International Space Station provides access to a persistent microgravity environment. environment of the ISS, the reduction of gravity-driven forces such as sedimentation and convection allow protein molecules to incorporate into the crystalline lattice more slowly and orderly, which can result in higher-quality crystals for analysis back on Earth.
Crystallizing Proteins Involved in Salmonella Contamination, Heart and Liver Disease, and DNA Repair
Researchers from the University of Toledo are crystallizing several proteins with important medical applications. The enzyme Salmonella typhimurium tryptophan synthase is not found in the human body but is important for bacterial growth. Infection from Salmonella, which most often occurs from eating food contaminated with the bacteria, affects more than 94 million people worldwide each year. An improved understanding of this enzyme’s structure could help scientists develop inhibitors to help control Salmonella contamination in the food industry.
The cytosolic aspartate aminotransferase enzyme in humans is a biomarker for heart attack or liver disease. A better understanding this enzyme’s structure could eventually lead to the development of compounds to help monitor patients receiving treatment for heart or liver disease.
The protein complex of RNase H protein and a single-stranded DNA binding protein plays an important role in DNA repair. Information about the structure of this protein complex could help researchers understand how to optimize the natural process of DNA repair to help prevent diseases caused by damaged DNA, such as cancer.
The University of Toledo research team hopes to produce crystals of these proteins that are large enough for neutron diffraction analysis. Neutron diffraction provides greater detail on a protein’s structure than traditional X-ray diffraction because it allows scientists to determine the position of hydrogen atoms within the structure. This is important because about half of the atoms in a protein are hydrogen. However, neutron diffraction requires large, high-quality crystals—which for some molecules can be difficult to obtain on Earth due to gravity-driven forces that disturb the crystallization process. For this reason, the ISS National Laboratory could provide a valuable platform for improving crystallization of such molecules.
Protein Crystallization Part Two
The University of Toledo experiment that launched on SpaceX CRS-18 is actually the second part of this team’s ISS National Laboratory investigation. The team first crystallized these proteins on the ISS National Laboratory in an experiment that launched on SpaceX CRS-15 in June 2018 and found that microgravity conditions did improve the growth of the crystals. In this second part of the investigation, the team hopes to further improve crystal quality using a slightly different method.
For this second experiment on the ISS, the team is replacing the hydrogen atoms in the proteins with deuterium, an isotope of hydrogen. An isotope is a variation of an element that contains the same number of protons in the atom’s nucleus but different numbers of neutrons, resulting in a different mass number but the same atomic number and chemical properties. Crystallization of the proteins with deuterium instead of hydrogen—an approach called protein perdeuteration—is useful because it does not require as large of crystals for neutron diffraction and could result in higher-resolution images.
Crystallizing Large Protein Complexes
The Dover Lifesciences research team is aiming to leverage microgravity conditions on the ISS for crystallization of two protein complexes that are difficult to crystallize on Earth: the enzyme glycogenin in complex with glycogen synthase 1 (an enzyme in muscle) and glycogen synthase 2 (a critical enzyme for glycogen synthesis in the liver).
Understanding the structure of these complexes could help scientists develop drugs that inhibit glycogen synthase. These types of drugs could be used to treat obesity—which affects more than 93.3 million adults in the U.S., according to the U.S. Centers for Disease Control and Prevention (CDC)—and rare genetic disorders that involve the storage of excess amounts of glycogen such as Cori disease, Pompe disease, and Lafora disease.
Drugs that inhibit glycogen synthase could also potentially be used alongside chemotherapy to treat cancer. To survive in a low-oxygen environment, many tumors increase the rate of glycogen synthesis, thus inhibiting glycogen synthase could make it harder for cancer cells to survive.
Crystallizing Cancer Therapeutics
Representatives from the ISS National Laboratory and Boeing pose for a photo with the MicroQuin team, winners of a 2018 MassChallenge Technology in Space PrizeA prize that provides grant funding for business startups participating in the MassChallenge startup accelerator program to conduct innovative research and technology development utilizing the ISS National Lab. The prize is funded by the Center for the Advancement of Science in Space, which manages the ISS National Lab, and Boeing..
Media Credit: MassChallenge
Researchers from MicroQuin seek to use microgravity to crystallize a membrane protein that plays an important role in the development of tumors and the survival of cancer cells. Ground-based crystallization of the protein has proven difficult, hindering structural determination. The team will crystallize the protein both alone and in complex with MicroQuin’s therapeutic drug to treat breast cancer. Results from this investigation could help the company both enhance its breast cancer drug as well as develop new therapeutics to treat other types of cancer. According to the CDC, one out of every four deaths in the U.S. is due to cancer, and breast cancer is the most common cancer in American women aside from some types of skin cancer.
The protein MicroQuin is crystallizing is also involved in the progression of Alzheimer’s, Parkinson’s, and type 2 diabetes and plays a role in bacterial infections, obesity, and ischemia-reperfusion injury (damage resulting from the return of blood supply to tissue after a period without oxygen). Insights gained from this research could help scientists better understand the protein’s role in such diseases and aid in the development of new targeted drugs.
Supporting Startups
The ISS National Laboratory investigations from Dover Lifesciences and MicroQuin were both funded through the MassChallenge program, a leading startup accelerator. Since 2014, the ISS National Laboratory has partnered with The Boeing Company to award grants to startups through an annual MassChallenge “Technology in Space Prize,” which supports startups with innovative ideas for research to be conducted onboard the ISS National Laboratory. The ISS National Laboratory and Boeing have together allocated more than $4.5 million in funding toward the prize.
Dover Lifesciences, a biotechnology startup based in Dover, Massachusetts, was one of three companies awarded the Technology in Space Prize in 2016. MicroQuin, a biotechnology startup based in Cambridge, Massachusetts, was one of two companies to receive the Technology in Space Prize in 2018. Learn more about MassChallenge and the Technology in Space Prize in the Upward feature, “Attracting Entrepreneurs to Space: MassChallenge Grantees Move Early-Stage Innovations Forward.”
Microgravity Molecular Crystal Growth
To establish sustainable platforms in low Earth orbit(Abbreviation: LEO) The orbit around the Earth that extends up to an altitude of 2,000 km (1,200 miles) from Earth’s surface. The International Space Station’s orbit is in LEO, at an altitude of approximately 250 miles. for ongoing crystallization research, the ISS National Laboratory aims to provide opportunities for crystallization investigations on every cargo resupply launch to the ISS, a rapid turnaround of samples, and hardware options to minimize preflight optimization steps. For more information about microgravity molecular crystal growth (MMCG), see the ISS National Laboratory MMCG overview.