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    Home > Biochemistry News > Biotechnology News > How does the protein inside the bacteria "cross the membrane"? The molecular mechanism of protein transport is analyzed.

    How does the protein inside the bacteria "cross the membrane"? The molecular mechanism of protein transport is analyzed.

    • Last Update: 2020-08-05
    • Source: Internet
    • Author: User
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    Why do people and animals get sick after contracting bacteria? Bacteria are usually single-celled microorganisms, one cell or one bacterium.
    some pathogenic bacteria in order to survive, reproduce and spread in the host body, will create some protein-like toxic factors in the cell core sugar, and secrete this protein out of the cell.
    even non-pathogenic bacteria, in order to adapt to their living environment, will secrete some protein. How do the proteins inside
    bacteria "cross the membrane"? This is a problem that the academic community has been trying to figure out.
    recently, Li Long, a researcher at Peking University's School of Life Sciences, and Gao Ning team edited the molecular mechanism of protein transport for an instant photo of the secreted protein "cross membrane".
    research published in the journal Nature Communications.
    signal peptides to do probe secretion protein "sweeping on the car" protein transport is a highly regulated process, there must be a mechanism to ensure that the cell can specifically need to be secreted protein transport out.
    ," Li Long said in an interview with Science and Technology Daily.
    as early as the 1970s, scholars speculated that cells had a substance that could identify the protein to be secreted to avoid the event of the oolong, which would not have to be secreted outside the cell.
    1972, the researchers found that some immunoglobulin precursors had 20 more amino acids than mature bodies.
    1975, the German scholar Blobel and others put forward the signal peptide hypothesis, the extra 20 amino acids called signal peptides, if the sequence of a protein in the cell contains signal peptides, it is equivalent to the protein "to be transferred" to the "bar code", gorgeous transformation into a secretion protein, and then there will be a "vehicle" carrying the protein to the inside of the cell membrane.
    the protein is then secreted to the extracellular through a "special channel" on the cell membrane.
    the hypothesis was subsequently confirmed by a series of experiments, and Blobel was awarded the 1999 Nobel Prize in Physiology or Medicine. What are
    "vehicles" that deliver proteins secreted? "It can be an ATP hydrolysis enzyme or a protein in bacteria, which we call SecA, and because it carries the secretion protein movement, it can be considered a 'motor protein'.
    " Li Long told reporters that signal peptides and secretion proteins have a one-to-one relationship, signal peptides are diverse, usually each secretion protein has a unique signal peptide "bar code."
    motor protein is not so "sophisticated", as long as there is a "bar code" protein can become its "passenger", no matter what kind of secretion protein.
    cell membrane sphiny, SecY, is responsible for scanning the secretion protein shipping from motor protein, identifying the successful opening of a special channel, releasing the secretion protein, and then the channel closes to restore the original phospholipid bimolecular layer structure of the cell membrane.
    Although the general process of protein transport has been identified, deeper questions still need to be explored, such as why motor proteins are able to identify signal peptides nonspecifically? Why do people find hydrophobic structures in all the signal peptides? Three proteins "one play" mutually identified regular Li Long, The Gao Ning team used an electronic cryo-microscope to "cross the membrane" of the protein to take a "photo" to answer the question of nonspecific binding.
    in fact, the moment of "capture" to protein "cross membrane" is very difficult, because the entire protein transport process is very rapid, in a second can complete the transport of more than a dozen proteins, so no one in the academic community has taken such a picture before.
    the two teams to find another way, to the cells "feed" the ATP analogue, the transport process locked in the "cross membrane" stage, and then the protein frozen down, with an electric mirror photo, will instantly permanently fix.
    the researchers' analysis found that motor proteins bind to the main chain of the protein secreted through the hydrogen bond and fold into a thin-layered structure.
    and the type of protein is determined by the amino acid sequence on its side chain, and the main chain sequence of different secreted proteins is consistent.
    this clearly explains why motor proteins are "not rejected" for the secretion of proteins.
    as to the hydrophobic structure of signal peptides, Li Long et al. discussed the issue in an earlier article published in the journal Nature.
    the phospholipid bimolecular layer of the cell membrane itself is hydrophobic structure, the channel protein SecY on the membrane can identify the same signal peptide with hydrophobic structure, and pin it to the cell membrane, and then the signal peptide enzyme in the cell will be the signal peptide and secretion protein cutting, secretion protein "trans membrane" out, the signal peptide is degraded, converted into basic amino acids, participate in the next cell activity.
    " The two studies are equivalent to two and a half pictures, stitched together into a complete 'cross-film' picture.
    " Li Long said, but the entire protein transport process is not just a "cross-film" moment of pictures can be explained, it is a dynamic process, it needs countless pictures to be a dynamic image to really reconstruct the true process of protein transport.
    this will be the next step for researchers.
    Source: Science Daily.
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