Re: [ccp4bb] Crystal Structures as Snapshots

[Roger Rowlett]

I believe the most justifiable assumption one can make is that crystal structures are likely to represent the least soluble conformations of a protein under the conditions of crystallization (which might be a broad range of conditions, including physiological). This can be quite vexing if you are studying an allosteric protein and one of the two conformations is typically much less soluble than the other. BTDT. I'm sure others have had the same experience. Having said that, the solvent content of protein crystals (which is close to that of cellular conditions), the observation of enzymatic activity in many protein crystals, and the *general* concordance of XRD and NMR structures of proteins (when both have been determined) leads one to believe that XRD structures are likely representative of physiologically relevant conformations. Cheers, _______________________________________ Roger S. Rowlett Gordon & Dorothy Kline Professor Department of Chemistry Colgate University 13 Oak Drive Hamilton, NY 13346 tel: (315)-228-7245 ofc: (315)-228-7395 fax: (315)-228-7935 email: rrowl...@colgate.edu On 2/10/2012 3:34 PM, Nat Echols wrote: On Fri, Feb 10, 2012 at 12:29 PM, James Stroud <xtald...@gmail.com> wrote: How could they not be snapshots of conformations adopted in solution? Packing billions of copies of an irregularly-shaped protein into a compact lattice and freezing it to 100K isn't necessarily representative of "solution", especially when your solution contains non-physiological amounts of salt and various organics (and possibly non-physiological pH too). -Nat