Vitamins doing gymnastics: Scientists capture first full image of vitamin B12 in action
Work by University of Michigan and MIT team yields new understanding of crucial reaction in the body and in CO2-scrubbing bacteria
You see it listed on the side of your cereal box and your multivitamin bottle. It's vitamin B12, part of a nutritious diet like all those other vitamins and minerals. But when it gets inside your body, new research suggests, B12 turns into a gymnast.
In a paper published in Nature, scientists from the University of Michigan Health System and the Massachusetts Institute of Technology report they have created the first full 3-D images of B12 and its partner molecules twisting and contorting as part of a crucial reaction called methyltransfer.
That reaction is vital both in the cells of the human body and, in a slightly different way, in the cells of bacteria that consume carbon dioxide and carbon monoxide. That includes bacteria that live in the guts of humans, cows and other animals, and help with digestion. The new research was done using B12 complexes from another type of carbon dioxide-munching bacteria found in the murky bottoms of ponds.
The 3-D images produced by the team show for the first time the intricate molecular juggling needed for B12 to serve its biologically essential function. They reveal a multi-stage process involving what the researchers call an elaborate protein framework – a surprisingly complicated mechanism for such a critical reaction.
U-M Medical School professor and co-author Stephen Ragsdale, Ph.D., notes that this transfer reaction is important to understand because of its importance to human health. It also has potential implications for the development of new fuels that might become alternative renewable energy sources.
"Without this transfer of single carbon units involving B12, and its partner B9 (otherwise known as folic acid), heart disease and birth defects might be far more common," explains Ragsdale, a professor of biological chemistry. "Similarly, the bacteria that rely on this reaction would be unable to consume carbon dioxide or carbon monoxide to stay alive – and to remove gas from our guts or our atmosphere. So it's important on many levels."
In such bacteria, called anaerobes, the reaction is part of a larger process called the Wood-Ljungdahl pathway. It's what enables the organisms to live off of carbon monoxide, a gas that is toxic to other living things, and carbon dioxide, which is a greenhouse gas directly linked to climate change. Ragsdale notes that industry is currently looking at harnessing the Wood-Ljungdahl pathway to help generate liquid fuels and chemicals.
In the images created by the team, the scientists show how the complex of molecules contorts into multiple conformations - first to activate, then to protect, and then to perform catalysis on the B12 molecule. They had isolated the complex from Moorella thermoacetica bacteria, which are used as models for studying this type of reaction.
The images were produced by aiming intense beams of X-rays at crystallized forms of the protein complex and painstakingly determining the position of every atom inside.
"This paper provides an understanding of the remarkable conformational movements that occur during one of the key steps in this microbial process, the step that involves the generation of the first in a series of organometallic intermediates that lead to the production of the key metabolic intermediate, acetyl-CoA," the authors note.
Senior author Catherine L. Drennan from MIT and the Howard Hughes Medical Institute, who received her Ph.D. at the U-M Medical School, adds, "We expected that this methyl-handoff between B vitamins must involve some type of conformational change, but the dramatic rearrangements that we have observed surprised even us."
A new molecular gel recipe developed at the University of Michigan is at the core of a prototype for a more accurate lead paint test.
The test makes it easy to see whether a paint chip contains more than the regulated 5,000 parts per million of the poisonous metal that was banned from pigme ... more
On your car windshield, ice is a nuisance. But on an airplane, a wind turbine, an oil rig or power line, it can be downright dangerous. And removing it with the methods that are available today--usually chemical melting agents or labor-intensive scrapers and hammers--is difficult and expens ... more
Serious flaws have been found in a decade's worth of studies about the best way to reduce greenhouse gas emissions and stabilize the climate.
The findings, from the University of Michigan, are released as world leaders at COP21 attempt to negotiate the globe's first internationally binding ... more
A new molecular gel recipe developed at the University of Michigan by Anne McNeil, Arthur F Thurnau Professor of Macromolecular Science, and is at the core of a prototype for a more accurate lead paint test.The new test is more clear and accurate than its counterparts. It consists of a vial ... more
It's a well-known fact that water, at sea level, starts to boil at a temperature of 212 degrees Fahrenheit, or 100 degrees Celsius. And scientists have long observed that when water is confined in very small spaces, its boiling and freezing points can change a bit, usually dropping by aroun ... more
A new technique developed by MIT researchers reveals the inner details of photonic crystals, synthetic materials whose exotic optical properties are the subject of widespread research.
Photonic crystals are generally made by drilling millions of closely spaced, minuscule holes in a slab of ... more
Graphene, a two-dimensional form of carbon in sheets just one atom in thick, has been the subject of widespread research, in large part because of its unique combination of strength, electrical conductivity, and chemical stability. But despite many years of study, some of graphene’s fundame ... more
MIT engineers have transformed spinach plants into sensors that can detect explosives and wirelessly relay that information to a handheld device similar to a smartphone.
Video: Melanie Gonick/MITInfrared/fluorescent images: Min Hao Wong more
“Experimenting with Thermopower Waves,” with MPC-CMSE 2015 Summer Scholar Stephen Gibbs and MIT Chemical Engineering graduate student Tianxiang (Albert) Liu. Recorded in the lab of Michael Strano, Carbon P. Dubbs Professor in Chemical Engineering, MIT. Recording and Editing, Denis Paiste, S ... more