The team has recently published two structural biology articles related to RecA family recombinases. One paper is to be published in the online, open-access journal PLoS ONE on September 12, 2007 and the other has been already published in the Nucleic Acids Research on Feb. 28, 2007.
Homologous recombination (HR) is a mechanism that repairs damaged DNA with perfect accuracy, it utilizes the homologous sequence from a partner DNA as a template. This process involves the bringing together of 2 DNA molecules, a search for homologous sequences, and exchange of DNA strands.
RecA family proteins are the central recombinases for HR. The family includes prokaryotic RecA, archaeal RadA, and eukaryotic Rad51 and Dmc1. They have important roles in cell proliferation, genome maintenance, and genetic diversity, particularly in higher eukaryotes. For example, Rad51-deficient vertebrate cells accumulate chromosomal breaks before death. Rad51 and its meiosis-specific homolog, Dmc1, are also indispensable for meiosis, a specialized cell cycle for production of gametes. Mammalian Rad51 and Dmc1 proteins are known to interact with tumor suppressor proteins such as BRCA2.
Since scientists discovered RecA family proteins, it has been assumed that RecA (and other homologs) forms only 61 right-handed filaments (six protein monomers per helical turn), and then hydrolyzes ATP to promote HR and recombinational DNA repair. Whereas a controversial puzzle came out, how the energy of ATP facilitating DNA rotation during the strand exchange reaction.
By X-ray crystallography and atomic force microscopy approaches, Dr. Wangs’ team provided the answer. They reported that archaeal Sulfolobus solfataricus RadA proteins can also self-polymerize into a 31 right-handed filament with 3 monomers per helical turn (reported in PLoS ONE) and a 43 right-handed helical filament with 4 monomers per helical turn (reported in Nucleic Acids Research).
Additional biophysical and biochemical analyses revealed that RecA family proteins may couple ATP binding and hydrolysis to the DNA strand exchange reaction in a manner that promotes clockwise axial rotation of nucleoprotein filaments. Specially, the 61 RadA helical filament undergoes clockwise axial rotation in 2 discrete 120° steps to the 31 extended right-handed filament and then to the 43 left-handed filament. As a result, all the DNA-binding motifs (denoted L1, L2 and HhH) in the RadA proteins move concurrently to mediate DNA binding, homology pairing, and strand exchange, respectively. Therefore, the energy of ATP is used to rotate not only DNA substrates but also the RecA family protein filaments.
This new model is in contrast to all current hypotheses, which overlooks the fact that RecA family proteins are flexible enough to form both right-handed and left-handed helical filaments. From this perspective, these researchers in Taiwan have opened a new avenue for understanding the molecular mechanisms of RecA family proteins.
Andrew Hyde | alfa
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