Isn't calcium-calmodulin one of the archetypical examples of the crystal structure probably not representing the solution structure (perhaps because the crystallization pH = 4.5)? Look at that linker helix--how stable can that be in solution? I don't think a single one of the NMR ca-calmodulin structures/conformers has the central helix like that.
Jacob On Fri, Feb 10, 2012 at 3:31 PM, Nat Echols <[email protected]> wrote: > Just to clarify - I actually think the original assumption that Jacob > posted is generally reasonable. But it needn't necessarily follow > that the conformation we see in crystal structures is always > representative of the solution state; given the extreme range of > conditions in which crystals grow, I would be surprised if there > weren't counter-examples. I'm not familiar enough with the literature > on domain swapping (e.g. diptheria toxin) to know if any of those > structures are crystal packing artifacts. > > On Fri, Feb 10, 2012 at 1:04 PM, George <[email protected]> wrote: >>>Packing billions of copies into a compact lattice >> Not so compact there is 40-80% water >>>freezing it to 100K >> We have frozen many times protein solutions in liquid nitrogen and then thaw >> and were working OK >>> non-physiological amounts of salt and various organics >> What is the amount of salt and osmotic pressure in the cell?? >>>non-physiological pH too >> What is the non-physiological pH too? I am sure that some enzymes they are >> not working in pH 7. Also most of the proteins they have crystallized in pH >> close to 7 so I would not say non-physiological. >> >> George >> >> PS There are lots of solution NMR structures as well supporting the >> physiological crystal structures >> >> >> -----Original Message----- >> From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of Nat >> Echols >> Sent: Friday, February 10, 2012 10:35 PM >> To: [email protected] >> Subject: Re: [ccp4bb] Crystal Structures as Snapshots >> >> On Fri, Feb 10, 2012 at 12:29 PM, James Stroud <[email protected]> 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 >> -- ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program email: [email protected] *******************************************
