Monday, June 21, 2010

Who is interested in ATP synthase?

Or - to be precise - where are they located?

About two years ago I made a world map overlay for visits of www.atpsynthase.info (04.2006-04.2008). In the last two years (06.2008-06.2010) the picture remained essentially the same:








Country                 
Visits






1.
United States
14,505






2.
United Kingdom
2,487






3.
Germany
2,271






4.
Canada
1,522






5.
Japan
1,183






6.
India
1,179






7.
France
640






8.
Taiwan
580






9.
Australia
539






10.
Netherlands
520

12 comments:

  1. is the ATP/H+ ratio the same whether the Fo-F1 ATP synthase operates in the forward or reverse mode?

    ReplyDelete
  2. Hi Christos,

    Yes, it seems so.

    See
    Steigmiller et al. PNAS 2008, pp3745-50
    Turina et al., EMBO J. 2003, pp418-26

    However, the ATP/H+ ratio issue is still a bit unclear (in my opinion)

    ReplyDelete
  3. Thanks. And what do you think about the recent results by Bernardi, showing that cyclophilin D binds on the lateral stalk (J Biol Chem. 2009 Dec 4;284(49):33982-8)? he used a cross-linker, how could that have been missed by others in the past (especially Walker?). Do you think that the Pi binding site that is masked by cypD is the same as the Pi binding site(s) that you mention in your review (Results Probl Cell Differ. 2008;45:279-308)?

    ReplyDelete
  4. The results are quite exciting, and I would really love to know, if there is some effect of CyD on the activity of the purified ATP synthase.

    >how could that have been missed by others in the past (especially Walker?)

    They say in the Discussion that "In the absence of Pi, the binding of CyPD is negligible". This might be one of the reasons.

    As for the Pi binding site, the one I mention in the 2008 review (which is involved in MgADP-inhibition) is actually the catalytic site. It would be very surprising, if binding of Pi to the catalytic sites is somehow "detected" by OSCP and alters its affinity to CyPD.

    ReplyDelete
  5. so, therefore you support only one Pi-binding site on ATPase, opposite from Penefsky's two Pi binding sites idea.

    ReplyDelete
  6. no, I think it is much more complicated.
    First, there are 3 cat sites on F1, and each can bind phosphate, and that leaves us with at least 3 Pi-binding sites. (However, the affinity might be quite different, similar to the affinity to nucleotides.)
    Second, I do not exclude the possibility of other Pi-binding sites. It could well be that the CyD binding is affected by Pi binding to a site that is not yet defined. In my previous comment I meant that it is difficult to imagine that binding of Pi to a cat site can effectively change the interaction of OSCP with CyD. I.e. it is probably some other Pi binding site responsible for that.

    ReplyDelete
  7. Why do you consider only OSCP? cypD was reported to interact with subunit d and b as well.

    ReplyDelete
  8. Same logic applies to both d and b: they are not part of the alpha3beta3gamma core that bears the Pi/nucleotide binding sites.
    Of course, one cannot exclude the possibility that Pi binding to a cat site leads to conformational changes in the F1 that are passed over to the second stalk (b,d, OSCP and other subunits) and alter the CyPD affinity.

    By the way, do you think that CyPD itself can be somehow sensitive to Pi concentration? I.e., is it possible that the change in affinity is caused no by Pi binding to FoF1, but by Pi effect on CyPD itself?

    ReplyDelete
  9. I don't know, but we can check that: we can incubate cypD with phosphate, and check if phosphate bound on it, and we can also check if cypD activity is altered by phosphate. If we see phosphate binding on cypD, then maybe worth trying to add cypD vs phosphate-bound cypD to ATPase, and see if the latter binds stronger. But I am not sure if cypD can bind to isolated ATPase. But perhaps we can just check OSCP only, not the whole ATPase.

    ReplyDelete
  10. Hello Boris,
    a question: does the ATPase use MgADP and Pi for synthesis and MgATP for hydrolysis, or free ADP and ATP for the respective processes?
    Bests, Christos

    ReplyDelete
  11. Hi Christos,

    FoF1 operates with Mg-nucleotides; without Mg there is no activity.

    Regards,

    Boris.

    ReplyDelete