Structural snapshots of Xer recombination reveal activation by synaptic complex remodeling and DNA bending
| Autor: | Ezgi Karaca, W. Marshall Stark, Orsolya Barabas, Banushree Kumar, Aleksandra Bebel |
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| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Models
Molecular 0301 basic medicine Protein Conformation QH301-705.5 Science chromosome segregation Biology Models Biological General Biochemistry Genetics and Molecular Biology Recombinases Chromosome segregation 03 medical and health sciences chemistry.chemical_compound X-Ray Diffraction Recombinase site-specific DNA recombination Biology (General) Gene X-ray crystallography Recombination Genetic Genetics General Immunology and Microbiology Helicobacter pylori Hydrolysis General Neuroscience Circular bacterial chromosome microbiology E. coli DNA replication Chromosome DNA General Medicine Biophysics and Structural Biology Cell biology 030104 developmental biology chemistry Structural biology Genes and Chromosomes genome maintenance Nucleic Acid Conformation Medicine Research Article Protein Binding |
| Zdroj: | 'eLife ', vol: 5, pages: e19706-1-e19706-23 (2016) eLife, Vol 5 (2016) eLife |
| ISSN: | 2050-084X |
| Popis: | Bacterial Xer site-specific recombinases play an essential genome maintenance role by unlinking chromosome multimers, but their mechanism of action has remained structurally uncharacterized. Here, we present two high-resolution structures of Helicobacter pylori XerH with its recombination site DNA difH, representing pre-cleavage and post-cleavage synaptic intermediates in the recombination pathway. The structures reveal that activation of DNA strand cleavage and rejoining involves large conformational changes and DNA bending, suggesting how interaction with the cell division protein FtsK may license recombination at the septum. Together with biochemical and in vivo analysis, our structures also reveal how a small sequence asymmetry in difH defines protein conformation in the synaptic complex and orchestrates the order of DNA strand exchanges. Our results provide insights into the catalytic mechanism of Xer recombination and a model for regulation of recombination activity during cell division. DOI: http://dx.doi.org/10.7554/eLife.19706.001 eLife digest Similar to humans, bacteria store their genetic material in the form of DNA and arrange it into structures called chromosomes. In fact, most bacteria have a single circular chromosome. Bacteria multiply by simply dividing in two, and before that happens they must replicate their DNA so that each of the newly formed cells receives one copy of the chromosome. Occasionally, mistakes during the DNA replication process can cause the two chromosomes to become tangled with each other; this prevents them from separating into the newly formed cells. For instance, the chromosomes can become physically connected like links in a chain, or merge into one long string. This kind of tangling can result in cell death, so bacteria encode enzymes called Xer recombinases that can untangle chromosomes. These enzymes separate the chromosomes by cutting and rejoining the DNA strands in a process known as Xer recombination. Although Xer recombinases have been studied in quite some detail, many questions remain unanswered about how they work. How do Xer recombinases interact with DNA? How do they ensure they only work on tangled chromosomes? And how does a protein called FtsK ensure that Xer recombination takes place at the correct time and place? Bebel et al. have now studied the Xer recombinase from a bacterium called Helicobacter pylori, which causes stomach ulcers, using a technique called X-ray crystallography. This enabled the three-dimensional structure of the Xer recombinase to be visualized as it interacted with DNA to form a Xer-DNA complex. Structures of the enzyme before and after it cut the DNA show that Xer-DNA complexes first assemble in an inactive state and are then activated by large conformational changes that make the DNA bend. Bebel et al. propose that the FtsK protein might trigger these changes and help to bend the DNA as it activates Xer recombination. Further work showed that the structures could be used to model and understand Xer recombinases from other species of bacteria. The next step is to analyze how FtsK activates Xer recombinases and to see if this process is universal amongst bacteria. Understanding how this process can be interrupted could help to develop new drugs that can kill harmful bacteria. DOI: http://dx.doi.org/10.7554/eLife.19706.002 |
| Databáze: | OpenAIRE |
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