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What is the structure of DNA polymerase III?

  1. Feb 10, 2017 #1
    According to Snustard and Simmons the structure of DNA polymerase III is the following, where the clamp loader( γ -δ complex ) is present on one side:


    But according to Lehninger the clamp loader is centrally located:


    Which one is right? Besides where can I find a correct diagrammatic representation of DNA polymerase III?
  2. jcsd
  3. Feb 12, 2017 #2


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    I'm not sure if either diagram can be called "right." Most of these diagrams are based on only limited information (e.g. which parts are directly touching eachother), but very often, it is difficult to directly image large multiprotein complexes such as DNA pol III. Information about the architecture of large complexes often comes from cryo-electron microscopy studies. A quick google search shows cryo-EM studies of parts of the complex (e.g. https://elifesciences.org/content/4/e11134) but I didn't find any of the entire complex.

    The Snustard and Simmons is probably right in that it present a minimal set of information about the complex without adding in unknown details (here the relative arrangement of the subunits is not meaningful, only the relative sizes and which subunits are directly contacting). The Lehninger diagram, however, involves a bit more imagination in thinking about how all of the pieces might fit together. This is definitely the one I've most often seen, though I'm not sure the extent to which it is based on actual evidence. Perhaps you could email the authors to see if they can provide any helpful references.
    Last edited: Feb 12, 2017
  4. Feb 12, 2017 #3
    Thank you for your advice, I really appreciate it.
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