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Analytical Chemistry

Cryo-EM On the March

Cryo-electron microscopy has been scoring some real successes lately as a structural biology technique. Anything that provides protein structures without having to crystallize proteins is of immediate interest, of course, and I think we can expect a lot more work in this area. Here’s a review on the current state of the art, for those who are into this sort of thing. I’d say that right now, getting solid high-resolution structures of random unknown proteins via EM is still an edge-of-what’s-possible technique, but it’s nowhere near as far out on the fringe as it used to be. Worth keeping an eye on.

7 comments on “Cryo-EM On the March”

  1. Morten G says:

    It’s still not a technique for intrinsically disordered proteins of which there are far too many in eukaryotes. Bastard proteins.

  2. luysii says:

    #1 Searching for a technique to show you ‘the’ structure of an intrinsically disordered protein segment is inherently quixotic.

  3. Morten G says:

    NMR and SAXS gives you some information but I think there is room for ridiculous amounts of improvement.
    But yes, the structure of an inherently disordered protein is a bit of an oxymoron. I think my thought was that the best subjects for cryo-EM also are the best subjects for crystallization.

  4. jbosch says:

    @Morton G.
    no, cryo-EM is excellent for complexes that are refractory to crystallization. Think 26S Proteasome for example. There are many subunits crystallized but not the whole thing.
    Also whole virus is “easier” with cyro-EM versus crystallization. Of course there are always exceptions. Best to be technique agnostic and use what works or combine different approaches.

  5. jbosch says:

    Along those lines, MicroED should become more streamlined (eventually).
    PMID 25303172 (free)
    Structure of catalase determined by MicroED.
    Nannenga BL, Shi D, Hattne J, Reyes FE, Gonen T.
    Elife. 2014 Oct 10;3:e03600. doi: 10.7554/eLife.03600.
    PMID: 24252878 (free)
    Three-dimensional electron crystallography of protein microcrystals.
    Shi D, Nannenga BL, Iadanza MG, Gonen T.
    Elife. 2013 Nov 19;2:e01345. doi: 10.7554/eLife.01345.

  6. Morten G says:

    @4 That’s not technique agnostic, that’s going “Dammit, crystallography failed. We’ll have to see what we can get with this shittier technique.”
    Cryo-EM should be first choice for a number of systems. If you want to look at antibody-protein interactions then I would say that cryo-EM should be your first priority.
    Big, homomeric, multimers with lots of internal symmetry would be great for cryo-EM but, most likely, crystallography can do those better. Until you get to virus size where everything is awful (which have been done both by cryo-EM and crystallography).

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