720 is not an impressive size for a stable interface, but it may do depending on molecule size and exact chemistry of the interface (h-bonds, salt bridges, disulphides, charges etc etc). Everything is subject to chemical environment and concentration, as usual. For these entries, PISA gives dissociation free energy of -1 kcal/mol. Given some +/- 5 kcal/mol estimated (guessed) accuracy of PISA, this may or may not be a stable thing. And yes, it has about 70-80% chances to be simply an artefact of crystal packing, according to some sort of derivations that I did in 2nd PISA paper in J.Comp.Chem. in January last year.
Having said all this, PISA is not an oracle and does not pretend to be correct in 100% of instances.
Eugene.
On 5 Sep 2011, at 10:14, Eleanor Dodson wrote:
> Like Jan, I find it very useful to sort out the clear cut cases. Otherwise it is easy to get things wrong..
>
> But isnt a buried surface area of 720 rather small for a stable interface? If there is other confirming evidence like 2 diff space groups then you feel more secure!!
>
> On 09/01/2011 02:27 PM, Yuri Pompeu wrote:
>> This is regarding Ethanīs point, particularly:
>> >2) the protein has crystallized as a monomer even though it
>> >[sometimes] exists in solution as a dimer. The interface
>> >seen in the crystal is not the "real" dimer interface and
>> >thus the PISA score is correct.
>> I see the same exact interface in a crystal of a close homologue that belongs to a different space group (hexagonal vs tetragonal system)
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