Copied from the microcosm
Scientists have built a model of the work of a nanoshritz
Russian scientists from the Southern Federal University (SFU) together with French colleagues have built a model that describes the principles of the device and operation of protein syringe-like nanomachines. Such structures are widely distributed among various biological objects, in particular viruses and some bacteria. The results obtained will be useful for the development of therapy for infectious diseases, in experiments in the field of genetic engineering and bioinformatics. The work was carried out with the support of a grant Published in the highly rated journal Nanoscale (Rochal et al., Accessibility between protein nanotubes in contractile ejection nanomachines).
People have always lived with nanomachines–complex or simple systems less than a ten-millionth of a meter in size. For example, viruses. These life forms are not able to reproduce outside the host cell, which they need to somehow penetrate. Millions of years of evolution have led to the emergence of special structures that help the virus to put its genetic material inside the cell: DNA or RNA. The most successful were syringe-like devices consisting of two tubes inserted into each other. When the outer cylinder shrinks, the inner one pierces the membrane, and information molecules are injected into the cell through it.
"Despite the fact that this mechanism has been known in general terms for several decades, relatively accurate data on the structure of two similar systems, the bacteriophage T4 bacterial virus and the pyocin R2 protein, the main "weapon" of Pseudomonas aeruginosa, have been obtained only in the last couple of years. Bacteriophage T4 uses a syringe-like nanomachine to inject viral DNA into its victim. The R-type pyocin proteins, on the contrary, do not inject any substance into the cell, but destroy it by making a "hole" in the shell and disturbing the electrochemical equilibrium. We have built a simple model using the example of bacteriophage T4 and pyocin R2, explaining the features of the device and operation of syringe–like nanomachines," says Sergey Roshal, Professor of the Department of Nanotechnology at the Faculty of Physics of the Southern Federal University.
Two tubular organelles of the nanomachine: a hollow "sword" and its cover – work harmoniously, ensuring successful introduction into the cell. When in contact with the surface of the victim's membrane, the outer tube, formed by weakly twisted spirals, undergoes restructuring, contracting and shortening. At the same time, a rigid "sword" hidden under the outer tube is included in the game: it is exposed and pierces the cage. The geometric transitions accompanying this mechanism are associated with the presence of a certain correspondence between the tubes in the device and dimensions (proportionality), first described by the authors of this work.
Any work requires energy expenditure, and all systems can perform it only at the expense of their internal "savings", which cannot be spent completely. This principle is also true for a syringe-like nanomachine. The stretched state of the cover has the greatest internal energy. The "sword" enclosed inside affects the geometry of the compression process, as if forcing the system to move to a position with minimal energy and do a lot of work. According to scientists, this relationship was described by a beautiful in its simplicity relationship between the parameters of the tubes (distance and angular displacement), changing when the nanomachine is triggered. The appearance of proportionality reduces both the interaction energy of the sword and the case themselves, and the internal energy of the system. The resulting gain allows you to increase the force with which the "sword" breaks through the cell membrane, making the work of the nanomachine more efficient.
"The study of the device and principles of functioning of the syringe-like nanomachine of bacteriophages is important for antibacterial therapy, especially in the case of the development of resistance to traditional antibiotics in harmful microorganisms. In addition, bacteriophages are a promising vector (nanocontainer) for the transfer of DNA sites in genetic engineering. We believe that the pattern of molecular nanomachines we have discovered can be observed in other similar, but still poorly studied nanoobjects. These are, for example, phage-like structures that help marine animals navigate in space, syringe-like cell organelles, and so on. In any case, the knowledge that the tubes of a molecular nanomachine can become commensurate after its operation will allow us to build more accurate structural models of these biological systems," concludes Sergey Roshal.
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