Dear all, thanks for the many answers sent privately or posted to CCP4BB! I cannot answer them all individually, and I also cannot answer the questions that some people asked, since I have not yet heard back from my colleague whose experiment that is. But I'm sure there are some options for him, which I summarize below:
a) nanodiscs -see http://en.wikipedia.org/wiki/Nanodisc b) DNA helicases oligomerize and look like a doughnut- not sure if that meets the disk-like shape, but if it does, there is a company called biohelix that will provide their helicases to the research community (not commercially available, but if you contact them and tell them you are doing research (biophysical experiment) and would like some protein, they will send you some. They use the helicases in making their products, but it's not the product they sell; however, they will provide some for research experiments. Here's the link - http://www.biohelix.com/products/helicases_customorder.asp c) I do not know if it is strictly what you are after but you may want to investigate Beta-propeller folds which are disk-like. Lots of lectins are Beta propellers. You may want to look at Sigma lectins and check which ones are beta-propellers. d) 2-cys peroxiredoxin might do the trick. i don't know if it's commercially availabe though... e) The chaperonin 10 from groes is a heptamer that could be described as a disk shape. It is available from Sigma (C7438) at a cost of £285 per 0.25mg, but you may get a discount on a bulk order. f) Hemopexin tetramer (http://www.sigmaaldrich.com/catalog/product/sigma/H9291?lang=es®ion=ES). g) hexameric CcmK4 (http://www.sciencemag.org/content/309/5736/936.full) and cysteine-crosslinked HIV-1 CA hexamer (http://www.ncbi.nlm.nih.gov/pubmed/19523676). Neither is commercially available, but the plasmids are available from the authors and express to ~50 mg/L in E.coli. h) I guess the insulin hexamer is pretty disk like? And it is cheap and easy to crystallise.. thanks again to all who responded! Kay
