From The DOE’s Brookhaven National Laboratory: “Structure of ‘Oil-Eating’ Enzyme Opens Door to Bioengineered Catalysts”
From The DOE’s Brookhaven National Laboratory
3.30.23
Karen McNulty Walsh
kmcnulty@bnl.gov
(631) 344-8350
Peter Genzer
genzer@bnl.gov
(631) 344-3174
Atomic level details reveal how enzyme selectively breaks hydrocarbon bonds suggesting bioengineering strategies for making useful chemicals.
Long-sought structure of oil-eating enzyme complex: A high-resolution cryo-EM map of the transmembrane two-protein complex (left) allows researchers to determine the locations of individual amino acids that make up the two proteins (right). AlkG (gray) serves and an electron carrier, transporting electrons from its single iron atom (red sphere) to the two iron atoms (red spheres) at the active site of the AlkB enzyme (colorful ribbon structure). The magenta structure below the active site is the substrate (see close-up views). Credit: BNL.
Scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have produced the first atomic-level structure of an enzyme that selectively cuts carbon-hydrogen bonds—the first and most challenging step in turning simple hydrocarbons into more useful chemicals. As described in a paper just published in Nature Structural & Molecular Biology [below], the detailed atomic level “blueprint” suggests ways to engineer the enzyme to produce desired products.
“We want to create a diverse pool of biocatalysts where you can specifically select the desired substrate to produce wanted and unique products from abundant hydrocarbons,” said study co-lead Qun Liu, a Brookhaven Lab structural biologist. “The approach would give us a controllable way to convert cheap and abundant alkanes—simple carbon-hydrogen compounds that make up 20-50 percent of crude oil—into more valuable bioproducts or chemical precursors, including alcohols, aldehydes, carboxylates, and epoxides.”
The idea is particularly attractive because most industrial catalytic processes used for alkane conversions produce unwanted byproducts and heat-trapping carbon dioxide (CO2) gas. They also contain costly materials and require high temperatures and pressure. The biological enzyme, known as AlkB, operates under more ordinary conditions and with very high specificity. It uses inexpensive earth-abundant iron to initiate the chemistry while producing few unwanted byproducts.
“Nature has figured out how to do this kind of chemistry with an inexpensive abundant metal and at ambient temperature and pressures,” said John Shanklin, chair of Brookhaven Lab’s Biology Department and a senior author on the paper. “As a result, there’s been massive interest in this enzyme, but a complete lack of understanding of its architecture and how it works—which is necessary to re-engineer it for new purposes. With this structure, we have now overcome this obstacle.”
From rancid oil to sweet success
Research team: Brookhaven Lab scientists Jin Chai, Qun Liu, John Shanklin, and Sean McSweeney stand in front of the cryo-electron microscope (cryo-EM) used to decipher the long-sought structure of an enzyme that selectively cleaves hydrocarbon bonds. Credit: BNL.
AlkB was discovered 50 years ago in a machine shop where bacteria were digesting cooling oil making it smell rancid. Biochemists discovered the bacterial enzyme AlkB as the factor enabling the microbes’ unusual appetite. Scientists have been interested in harnessing AlkB’s hydrocarbon-chomping ability ever since.
Over the years, studies revealed that the enzyme sits partially embedded in the bacteria’s membranes, and that it operates in conjunction with two other proteins. Shanklin and Liu—and scientists elsewhere—tried solving the enzyme’s structure using x-ray crystallography. That method bounces high-intensity x-rays off a crystallized version of a protein to identify where the atoms are. But membrane proteins like AlkB are notoriously difficult to crystallize—especially when they are part of a multi-protein complex.
“We couldn’t get high enough resolution,” Liu said.
Then in early 2021, Brookhaven opened its new cryo-electron microscope (cryo-EM) facility, the Laboratory for BioMolecular Structure (LBMS). The scientists used a cryo-EM, which does not require a crystallized sample, to take pictures of a few million individual frozen protein molecules from many different angles. Computational tools then sorted through the images, identified and averaged the common features—and ultimately generated a high-resolution, three-dimensional map of the enzyme complex. Using this map, the scientists then pieced together the known atomic-level structures of the individual amino acids that make up the protein complex to fill in the details in three dimensions.
Identifying the right conditions to stabilize the transmembrane region of the enzyme and maintain the structural details was a challenge that required a good deal of trial and error. Shanklin credits Jin Chai, one of the researchers in his lab, “for his commitment and determination to solving this puzzle.”
Structure reveals how enzyme works
The detailed structure shows exactly how AlkB and one of the two associated proteins (AlkG) work together to cleave carbon-hydrogen bonds. In fact, the solved structure contained an unexpected bonus: a substrate alkane molecule that was trapped in the enzyme’s active site cavity.
Active site: These closeups of the AlkB active site show how nine histidine amino acids (denoted as “H” in the left image) form a cavity (gray shaded region, right). This cavity guides the substrate (magenta) to the active site (near the two iron, Fe, atoms) in a single orientation, where only the terminal carbon-hydrogen bond can be cleaved. Modifying the enzyme to change the shape of this cavity could allow the enzyme to attack different C-H bonds. Credit: BNL.
“Our structure shows how the amino acids that make up this enzyme form a cavity that orients the hydrocarbon substrate so that just one specific carbon-hydrogen bond can approach the active site,” Liu said. “It also shows how electrons move from the carrier protein (AlkG) to the di-iron center at the enzyme’s active site, allowing it to activate a molecule of oxygen to attack this bond.”
Shanklin suggests thinking of the enzyme as a bond-cutting machine like a circular saw: “How you hold the alkane with respect to the enzyme’s di-iron center determines how the activated oxygen interacts with the hydrocarbon. If you guide the end of the alkane against the activated oxygen, it’s going to initiate some chemistry on that last carbon.
“The engineering we want to do is to change the shape of the active site cavity so we can have the substrate (or a different substrate) approach the activated oxygen at different angles and in different C-H bond locations to perform different reactions.”
In nature, the scientists noted, a third protein not included in this structure (AlkT) provides the electrons to AlkG, the carrier protein. The carrier protein then transports the electrons to the two iron atoms that activate oxygen at AlkB’s active site. Replacing that electron donating protein with an electrode to supply electrons would be simpler and less costly than using the biological electron donor, they suggest.
DOE just funded the team’s proposal to develop such ‘Transformative Biohybrid Diiron Catalysts for C-H Bond Functionalization,’ based in part on this preliminary structural work.
“This structure and our knowledge of how the AlkG/AlkB complex works, puts us in a great position to bioengineer this enzyme to select which carbon-hydrogen bond gets activated in a variety of substrates and to control the electrons and oxygen to re-engineer its selectivity,” Liu said.
This work was supported by the DOE Office of Science (BES) and by Laboratory Directed Research and Development funds at Brookhaven Lab. LBMS is supported by the DOE Office of Science (BER). This research also used resources of Brookhaven Lab’s Center for Functional Nanomaterials (CFN), which is a U.S. Department of Energy Office of Science (BES) User Facility.
Nature Structural & Molecular Biology
See the science paper for instructive material with images.
See the full article here .
Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.
five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.
Stem Education Coalition
One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.
BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.
Major programs
Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:
Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics
Operation
Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.
Foundations
Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.
Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.
On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).
Research and facilities
Reactor history
In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.
Accelerator history
In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.
The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).
BNL Alternating Gradient Synchrotron (AGS).
The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.
In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.
The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.
The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].
BNL National Synchrotron Light Source.
After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider (CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.
On January 9, 2020, it was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

Electron-Ion Collider (EIC) at DOE’s Brookhaven National Laboratory to be built inside the tunnel that currently houses the Relativistic Heavy Ion Collider [RHIC]. Credit: BNL.
In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.
Other discoveries
In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.
Major facilities
Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.
Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.
BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.
Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.
Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.
Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.
Off-site contributions
It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Large Hadron Collider(LHC). Credit: CERN.
The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map. Credit: CERN.
It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] near Geneva, Switzerland.
Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.
DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.
Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.
Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota.
Reply