New details of the composition and structure of a needlelike protein complex on the surface of certain bacteria may help scientists develop new strategies to thwart infection.
The research, conducted in part at the U.S. Department of Energy's Brookhaven National Laboratory, will be published April 26, 2009, in the advance online edition of Nature Structural & Molecular Biology.
The scientists were studying a needlelike protein complex known as a "type III secretion system," or T3SS, on the surface of Shigella bacteria, a cause of dysentery. The secretion system is a complex protein structure that traverses the bacterial cell membrane and acts as a biological syringe to inject deadly proteins into intestinal cells. These proteins rupture the cell's innards, leading to bloody diarrhea and sometimes death. Similar secretion systems exist in a range of other infectious bacteria, including those that cause typhoid fever, some types of food poisoning, and plague.
"Understanding the 3D structure of these secretion proteins is important for the design of new broad-spectrum strategies to combat bacterial infections," said study co-author Joseph Wall, a biophysicist at Brookhaven Lab.
Previous studies of the type III secretion system have revealed that it is composed of some 25 different kinds of proteins assembled into three major parts: a "bulb" that lies within the bacterial cell, a region spanning the inner and outer bacterial membranes, and a hollow, largely extracellular "needle." But to understand how the parts work together to secrete proteins, the scientists required higher-resolution structural information, and knowledge of the chemical makeup and arrangement of the components.
Using a combination of scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM), the scientists have now revealed new details of the "needle complex" structure.
"STEM and the other techniques work in complementary ways," said Wall, who designed and runs the STEM facility at Brookhaven Lab. By itself, STEM cannot reveal a structure, but it gives very accurate sizes of the molecules making up particular parts, which helps scientists hone in on the structure hinted at by the other techniques. STEM also allows only good, intact molecules to be selected for analysis, which avoids errors inherent in bulk measures of mixtures of intact and broken complexes, a problem that may have affected previous analyses.
"Our reconstruction shows an overall size, shape and major sub-component arrangement consistent with previous studies," said Wall. "However, the new structure also reveals details of individual subunits and their angular orientation, which changes direction over the structure's length. We now see 12-fold symmetric features and details of connections between sub-domains both internally and externally throughout the 'needle' base."
The more accurate model therefore shows how the different parts of the injection machine fit together and may fit with other bacterial components that provide the engine to drive injection. These are important steps toward developing a detailed understanding of how the injection machine works, and to developing inhibitors that can prevent bacterial infections.
Although STEM was built more than 25 years ago, it remains a state-of-the-art tool for accurately determining the stoichiometry and homogeneity of biological complexes. It is one of the unique tools that Brookhaven Lab provides to the scientific community.
In the case of this study, said lead author Ariel Blocker of Oxford University and the University of Bristol, UK, "The STEM experiment was key because it provided unique and independent information that allowed the narrowing down of potential symmetries within the structure to a small set of testable possibilities."
Co-authors on this study include: Julie L. Hodgkinson of Oxford University and Medical School Hanover, Germany; Ariel J. Blocker of Oxford and University of Bristol, UK; Ashley Horsley, David Stabat, Steven Johnson, and Susan M. Lea, all of Oxford; Joseph S. Wall and Martha Simon of Brookhaven Lab; and Paula C. A. da Fonseca and Edward P. Morris of Chester Beatty Laboratories, UK.
The research was funded by the UK Medical Research Council, and a Guy G. F. Newton Senior Research Fellowship. The STEM laboratory at Brookhaven Lab is supported by the U.S. National Institutes of Health and the Department of Energy's Office of Science (Office of Biological and Environmental Research) and by fee-for-service support. For information about fees, contact Joseph Wall, email@example.com, or download [http://www.biology.bnl.gov/stem/stem_charges.pdf] this pdf file. For additional information about STEM, click [http://www.biology.bnl.gov/stem/stem.html] here.
One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), 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. Brookhaven is operated and managed for DOE's Office of Science by Brookhaven Science Associates, a limited-liability company founded by the Research Foundation of State University of New York on behalf of Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy