Ed (and Ivan) Peter Sun and colleagues published two papers where they show that crystallization conditions for protein-protein complexes are strongly biased towards PEG-based rather than high-salt or organic-solvent-based conditions. This includes antibody-antigen complexes.
http://www.ncbi.nlm.nih.gov/pubmed/16699187 http://scripts.iucr.org/cgi-bin/paper?do0016 I have heard anecdotally that the same is true of protein-peptide and protein-small molecule complexes, although I don't know of any systematic study. Can anyone shed light on this? I guess we can look in the Marseilles database Best wishes to all Patrick On Thu, Jul 28, 2011 at 2:32 PM, Ed Pozharski <epozh...@umaryland.edu> wrote: > > On Thu, 2011-07-28 at 05:07 +0100, Sean Seaver wrote: > > Spoiler - Fabs like ammonium sulfate. > > Not really - in my hands the ammonium sulfate was one hit out of 7. > > While Ivan's question is about Fab complexes with protein antigen, I > think it brings up a more general question of protein class-dependent > crystallization bias. While some general trends exist for classes of > biopolymers (e.g. MPD is number one precipitant for DNA; protein:DNA > complexes tend to crystallize in PEG-based conditions), a general idea > of assigning a preferred precipitant to a protein class is, imho, > pointless. Fabs are a good example - one would think that with half of > the protein more or less the same in all instances some general trends > should exist. And perhaps they do, as this > > http://scripts.iucr.org/cgi-bin/paper?S0907444999016224 > > seems to suggest. But alas, Fab crystallization conditions, once you > look into it, appear to be just as diverse as the same for proteins in > general. Crystallization conditions may change radically upon point > mutation, so why would one expect that a class of proteins sharing some > 50% identity will show unusual love for PEG, ammonium sulfate, sodium > malonate or any other "miracle precipitant"? > > Consider this. Thanks to great engineering at the Douglas Instruments, > we can routinely set up ~1000 drops for a given protein. If one of them > shows a crystalline shower, we celebrate. To me, the fact that we try > wrong crystallization conditions 99.9% of the time, proves that any > attempt to predict crystallization conditions beyond vague things like > "keep pH close to protein pI", "sodium malonate is cool", "PEG and > ammonium sulfate are two most successful precipitants in history of > protein crystallography", etc., is futile. Time wasted on looking into > what is the most common precipitant for a particular class of proteins > is better spent on setting up more trays. > > Cheers, > > Ed. > > -- > Oh, suddenly throwing a giraffe into a volcano to make water is crazy? > Julian, King of Lemurs -- patr...@douglas.co.uk Douglas Instruments Ltd. DouglasHouse, EastGarston, Hungerford, Berkshire, RG177HD, UK Directors: Peter Baldock, Patrick Shaw Stewart http://www.douglas.co.uk Tel: 44 (0) 148-864-9090 US toll-free 1-877-225-2034 Regd. England 2177994, VAT Reg. GB 480 7371 36