Archaea are motile by the rotation of the archaellum. The archaellum switches between clockwise and counterclockwise rotation, and movement along a chemical gradient is possible by modulation of the switching frequency. This modulation involves the response regulator CheY and the archaellum adaptor protein CheF. In this study, two new crystal forms and protein structures of CheY are reported. In both crystal forms, CheY is arranged in a domain-swapped conformation. CheF, the protein bridging the chemotaxis signal transduction system and the motility apparatus, was recombinantly expressed, purified and subjected to X-ray data collection.

The structure of a 22-base-pair RNA helix with mismatched pyrimidine base pairs is reported. The helix contains two symmetry-related CUG sequences: a triplet-repeat motif implicated in myotonic dystrophy type 1. The CUG repeat contains a U–U mismatch sandwiched between Watson–Crick pairs. Additionally, the center of the helix contains a dimerized UUCG motif with tandem pyrimidine (U–C/C–U) mismatches flanked by U–G wobble pairs. This region of the structure is significantly different from previously observed structures that share the same sequence and neighboring base pairs. The tandem pyrimidine mismatches are unusual and display sheared, cross-strand stacking geometries that locally constrict the helical width, a type of stacking previously associated with purines in internal loops. Thus, pyrimidine-rich regions of RNA have a high degree of structural diversity.

Cytisine, a natural product with high affinity for clinically relevant nicotinic acetylcholine receptors (nAChRs), is used as a smoking-cessation agent. The compound displays an excellent clinical profile and hence there is an interest in derivatives that may be further improved or find use in the treatment of other conditions. Here, the binding of a cytisine derivative modified by the addition of a 3-(hydroxypropyl) moiety (ligand 4) to Aplysia californica acetylcholine-binding protein (AcAChBP), a surrogate for nAChR orthosteric binding sites, was investigated. Isothermal titration calorimetry revealed that the favorable binding of cytisine and its derivative to AcAChBP is driven by the enthalpic contribution, which dominates an unfavorable entropic component. Although ligand 4 had a less unfavorable entropic contribution compared with cytisine, the affinity for AcAChBP was significantly diminished owing to the magnitude of the reduction in the enthalpic component. The high-resolution crystal structure of the AcAChBP–4 complex indicated close similarities in the protein–ligand interactions involving the parts of 4 common to cytisine. The point of difference, the 3-(hydroxypropyl) substituent, appears to influence the conformation of the Met133 side chain and helps to form an ordered solvent structure at the edge of the orthosteric binding site.

The true identity of the protein found in the crystals reported by Bondoc et al. [(2019), Acta Cryst. F75, 646–651] is given.

Mycobacterium tuberculosis produces glycogen (also known as α-glucan) to help evade human immunity. This pathogen uses the GlgE pathway to generate glycogen rather than the more well known glycogen synthase GlgA pathway, which is absent in this bacterium. Thus, the building block for this glucose polymer is α-maltose-1-phosphate rather than an NDP-glucose donor. One of the routes to α-maltose-1-phosphate is now known to involve the GlgA homologue GlgM, which uses ADP-glucose as a donor and α-glucose-1-phosphate as an acceptor. To help compare GlgA (a GT5 family member) with GlgM enzymes (GT4 family members), the X-ray crystal structure of GlgM from Mycobacterium smegmatis was solved to 1.9 Å resolution. While the enzymes shared a GT-B fold and several residues responsible for binding the donor substrate, they differed in some secondary-structural details, particularly in the N-terminal domain, which would be expected to be largely responsible for their different acceptor-substrate specificities.

For those who think that global warming is a 21st-century phenomenon, Scott Wing, a scientist at the Smithsonian’s National Museum of Natural History, has news about the past.

The post Fossils Show Prehistoric Global Warming appeared first on Smithsonian Insider.

A recent study of dog bones excavated from archaeological sites on the Channel Islands of California has cast new light on the past ecology of the islands and the impact that domestic dogs--brought to the islands by Native Americans more than 6,000 years ago—may have once had on the islands’ animals and ecosystems.

The post Dog bones reveal ecological history of California’s Channel Islands appeared first on Smithsonian Insider.

New measurements show that the Milky Way is bigger and more massive than previous data suggested, putting us on equal footing with our neighbor. Specifically, the Milky Way is 15 percent larger in size and contains 50 percent more mass. That is the cosmic equivalent of a 5-foot-5, 140-pound man suddenly bulking up to the size of a 6-foot-3, 210-pound NFL linebacker.

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Scientists at the Smithsonian Institution examined the feather remains from the Jan. 15, 2009, US Airways Flight 1549 bird strike to determine not only the species, but also that the Canada geese involved were from a migratory, rather than resident, population. This knowledge is essential for wildlife professionals to develop policies and techniques that will reduce the risk of future collisions. The team’s findings were published in the journal “Frontiers in Ecology and the Environment” in June.

The post Scientists Determine Geese Involved in Hudson River Plane Crash Were Migratory appeared first on Smithsonian Insider.

In southeastern Greenland, two rivers of ice named Helheim and Kangerdlugssuaq flow in spurts and starts toward the coast. They are much like any other […]

The post Astrophysical Observatory scientists are monitoring the mysterious movements of glaciers appeared first on Smithsonian Insider.

When songwriter Oscar Hammerstein penned the lyrics “fish gotta swim, birds gotta fly,” he clearly did not have the ratites in mind. Large flightless birds, the ratites include ostriches, emus, rheas and cassowaries, along with kiwis and several extinct species.

The post DNA evidence is rearranging the branches of the avian family tree appeared first on Smithsonian Insider.

While studying bats recently at the Academy of Natural Sciences in Philadelphia, Smithsonian mammalogist Kristofer Helgen discovered a new species of flying fox bat from […]

The post Smithsonian Scientist Discovers Two New Bat Species Hiding in Museum Collections for More Than 150 Years appeared first on Smithsonian Insider.

Already under siege from overfishing, disease and poor water quality, the oyster population in the Chesapeake Bay today stands at 2 percent of what it was in colonial times. Now, new data show that rising acidity in the Bay will have a negative impact on oyster shells.

The post Rising acidification of estuary waters spells trouble for Chesapeake Bay oysters appeared first on Smithsonian Insider.

New observations by the Smithsonian’s Submillimeter Array, a radio telescope atop Mauna Kea in Hawaii, are shedding light on planet formation. The array provides sharp views by combining eight antennas into the equivalent of a single, large telescope. It can resolve details as small as a dime seen from seven miles away.

The post Cosmic “baby photos” of distant solar systems lend insight as to how planets form appeared first on Smithsonian Insider.

A Smithsonian Institution biologist, working with the Natural History Unit of the British Broadcasting Corp., has discovered a new species of giant rat on a film-making expedition to a remote rainforest in New Guinea.

The post New species of giant rat discovered in crater of volcano in Papua New Guinea appeared first on Smithsonian Insider.

Determining the locations of future highways and roads in countries with tropical rainforests will be the greatest single factor in influencing future forest loss, fragmentation and degradation. In broad terms, roads can be thought of as the enemies of rainforests. By spreading people out across the forest, roads inherently promote rapid and widespread deforestation.

The post Roads kill rainforests. Stop them now, say Smithsonian biologists appeared first on Smithsonian Insider.

Scientists from the Smithsonian Migratory Bird Center at the National Zoo have taken blood samples from thousands of birds and mosquitoes in an effort to track the progress of the West Nile Virus in the eastern United States. Come along in this video as Smithsonian scientists net birds living in downtown Washington, D.C., extract small amounts of blood, and then release them back into the "wild."

The post Video: Common birds in Washington, D.C. are helping Smithsonian scientists track intensity of the West Nile Virus appeared first on Smithsonian Insider.

A major new exhibition hall dedicated to the discovery and understanding of human origins will open next year at the Smithsonian's National Museum of Natural History: The David H. Koch Hall of Human Origins

The post Hall of Human Origins to open at Smithsonian’s Natural History Museum, March 17, 2010 appeared first on Smithsonian Insider.

The John Marshall Ju/'hoan Bushman Film and Video Collection, 1950-2000, was among 35 documentary heritage items of exceptional value added to UNESCO’s Memory of the World Register in 2009.

The post John Marshall Ju/’hoan Bushman Film and Video Collection added to UNESCO register appeared first on Smithsonian Insider.

Native to Africa and Madagascar, females of the species have a body length of 1.5 inches and a leg span of 4 to 5 inches. Males are tiny in comparison.

The post Females are giants in newly discovered species of golden orb weaver spider appeared first on Smithsonian Insider.

The National Zoo has been awarded a grant from the U.S. Fish and Wildlife Service to establish a captive population of the Virginia big-eared bat at the National Zoo’s Conservation & Research Center near Front Royal, Va. Only 15,000 Virginia big-eared bats remain living in caves in West Virginia, Virginia, Kentucky and North Carolina, and these are threatened by the white-nose syndrome.

The post In face of crisis, National Zoo to start captive population of Virginia big-eared bats appeared first on Smithsonian Insider.

There are several hypotheses about how amphibian chytrid has spread around the world, but the trade in amphibians for food, bait, pets and laboratory animals has been identified as the most likely mode of spread

The post Trade in frog legs may spread diseases deadly to amphibians appeared first on Smithsonian Insider.

It is one of the largest and most productive estuaries in the world, yet dramatic changes are in store for the Chesapeake Bay in coming […]

The post Climate change may drastically alter Chesapeake Bay, scientists say appeared first on Smithsonian Insider.

The Smithsonian’s National Air and Space Museum recently obtained two monumental instruments on loan from NASA’s Goddard Space Flight Center.

The post New Acquisition: Corrective instruments from the Hubble Space Telescope appeared first on Smithsonian Insider.

Dennis W. Kelly has been named director of the Smithsonian’s National Zoo in Washington, D.C., effective Feb. 15, 2010.

The post Dennis Kelly Named Director of the Smithsonian’s National Zoo appeared first on Smithsonian Insider.

Recently, researchers from Boston University and the Smithsonian Tropical Research Institute in Panama have been taking a closer look at the vibrations that red-eyed treefrog embryos use as cues to trigger early hatching. They discovered that treefrog embryos can evaluate different features of vibrations.

The post Researchers discover treefrog embryos can evaluate different features of vibrations appeared first on Smithsonian Insider.

Chi Cygni pulses once every 408 days. At its smallest diameter of 300 million miles, it becomes mottled with brilliant spots as massive plumes of hot plasma roil its surface. As it expands, Chi Cygni cools and dims, growing to a diameter of 480 million miles—large enough to engulf and cook our solar system out to the asteroid belt.

The post Distant, dying star gives astronomers preview of the fate of our Sun appeared first on Smithsonian Insider.

For the first time in its history, the National Zoo has bred strawberry dart frogs (Oophaga pumilio), which are known primarily for their vibrant colors and poisonous skin. These frogs also stand out among others because of their dedication to their young as they undergo metamorphosis from egg to tadpole to frog.

The post Strawberry dart frogs bred at National Zoo for first time in Zoo’s history appeared first on Smithsonian Insider.

In their laboratory, scientists from the University of Cambridge, the University of Southampton and the Smithsonian Tropical Research Institute in Panama, observed as a number of adult locusts walked along a horizontal ladder. After covering the right or left eye of an insect, the scientists observed a significant increase in the error rate of rungs missed by the front leg on the side of the covered eye.

The post For first time, scientists prove locusts use vision to place their legs when walking appeared first on Smithsonian Insider.

Timing was critical because female giant pandas ovulate only once a year. A short period of two to three days around ovulation is the only time she is able to conceive. Gestation typically lasts from 90 to 185 days.

The post Smithsonian scientists give giant pandas a helping hand at reproduction appeared first on Smithsonian Insider.

Koenig and his colleagues examined an area of space called W5, which lies about 6,500 light-years away toward the constellation Cassiopeia—about 6 trillion miles. Their research indicates the prospects for hypothetical alien life there are disappointing.

The post Planets form around many star types, but intelligent life is probably rare appeared first on Smithsonian Insider.

A meteorite that crashed through the roof of a Lorton, Va., doctors’ office on Monday, Jan. 18, 2010 was recently identified by scientists in the […]

The post Meteorite that fell in Lorton, Va., identified by Smithsonian scientists appeared first on Smithsonian Insider.

Birds do it. Bees do it. And in a laboratory in northern California, scientists using bumblebees recently figured out the best way to measure it--vertical lift!

The post Laboratory tests reveal precise way to measure vertical lift in bumblebees and other small insects and birds appeared first on Smithsonian Insider.

A new study published in the Feb. 2 issue of the Proceedings of the National Academy of Sciences indicates that forests in the Eastern United […]

The post Smithsonian ecologists discover forests are growing at a faster rate appeared first on Smithsonian Insider.

White, who was a student at Columbian College from Accomack County, Va., died of pneumonia and complications from a mitral heart defect. When his coffin was unearthed, his identity was a deep mystery.

The post Remains of William Taylor White (1837-1852) donated to Smithsonian with his coffin and clothing appeared first on Smithsonian Insider.

Finding this stellar relic wasn’t easy. It is 60,000 times dimmer than the faintest star visible to the unaided eye. The team also had to distinguish it from many surrounding stars that aren’t so old. Just like an archaeological dig, the hunt succeeded through a combination of patience and clever use of technology.

The post Ancient star discovered through patience and clever use of technology appeared first on Smithsonian Insider.

Scientists from the Smithsonian Museum Conservation Institute, the University of Valencia in Spain and the University of Minnesota, recently made an important observation regarding charcoals […]

The post Fungi still visible in wood charcoal centuries after burning appeared first on Smithsonian Insider.

The Stephen L. Wood collection brings the collection of bark beetles held in the Natural History Museum’s Department of Entomology to an impressive 180,000 specimens, making it one of the most extensive collections in world.

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About as thick as a standard dictionary, this turtle’s shell may have warded off attacks by the Titanoboa, thought to have been the world’s biggest snake, and by other, crocodile-like creatures living in its neighborhood 60 million years ago.

The post Newly discovered prehistoric turtle co-existed with world’s biggest snake appeared first on Smithsonian Insider.

Eric Silver of SAO is pursuing innovative and interdisciplinary uses of his technique for chemical imaging at the cellular level.

The post Technology developed for X-ray astronomy is being adapted to study cancer cells appeared first on Smithsonian Insider.

The rescue pods will be part of the project’s Amphibian Rescue Center at Summit Municipal Park, which will also include a lab with a quarantine facility.

The post Shipping industry sends help as project in Panama tackles amphibian crisis appeared first on Smithsonian Insider.

Based on current hormone analyses, and not having seen a fetus during the ultrasound exams, Zoo researchers have determined that Mei Xiang experienced a pseudopregnancy.

The post National Zoo’s giant panda Mei Xiang is not pregnant appeared first on Smithsonian Insider.

Long before dawn on a recent morning, Katie Milton and a group of stalwart volunteers, each armed with flashlight and compass, spread out into the jungle to take up positions at 35 listening stations marked on maps of the island.

The post Census reveals 1,200 howler monkeys living on Barro Colorado Island appeared first on Smithsonian Insider.

More than 25 years ago, researchers at the Smithsonian Environmental Research Center's Fish and Invertebrate Ecology Lab began taking weekley surveys of the species that make their way in and out of Muddy Creek.

The post Net survey: For quarter century, scientists have been counting creatures traveling Chesapeake Bay tributary appeared first on Smithsonian Insider.

“We are working as hard as we can to find and identify frogs before the disease reaches them, and to learn more about a disease that has the power to ravage an entire group of organisms,” said Roberto Ibanez, research scientist at STRI and local director of the Panama Amphibian Rescue and Conservation Project.

The post Two new frog species discovered in Panama’s fungal war zone appeared first on Smithsonian Insider.

This innovative facility will be at the front line of Earth defense by searching for "killer" asteroids and comets. It will map large portions of the sky nightly, making it an efficient sleuth for not just asteroids but also supernovae and other variable objects.

The post Super sensitive telescope will detect “killer” asteroids and comets on collision course with Earth appeared first on Smithsonian Insider.

The new study suggests that echolocation calls also serve a social function--bats listen to the ultrasonic calls of other bats to identify roost mates, bats of the same species, members of the opposite sex and intruders to their territory.

The post Scientists find ultrasonic calls of bats also serve a social function appeared first on Smithsonian Insider.

Unless action is taken now, coral reefs and many of the animals that depend on them may cease to exist within the next 40 years, causing the first global extinction of a worldwide ecosystem during current history.

The post Scientists establish first frozen repository of Hawaiian coral appeared first on Smithsonian Insider.