Pankaj,

Again a few remarks:

-          Is Pisa predicting a tetramer for the P6522 crystals, but not for the D32 crystals?

-          Or is the putative tetramer present in both crystal forms?

-          Would some of the putative tetramer contacts become stronger upon protonation at low pH? In that case one could consider changing the residues involved to their protonated counterparts (e.g. Asp->Asn).

 

Herman

 

Von: CCP4 bulletin board [mailto:[log in to unmask]] Im Auftrag von pankaj sharma
Gesendet: Donnerstag, 10. September 2015 14:01
An: [log in to unmask]
Betreff: Re: [ccp4bb] How different space groups affect interaction between symmetry mates of a protein and its mutant

 

Thanks for your valuable suggestions, to be more precise this protein is biologically dimeric in nature and we are getting same result through PISA. But during stressed conditions this wt protein forms tetramers (As seen in native gel), further mutant protein also forms tetramers under normal conditions (i.e. in the absence of stress, like low pH), so can we assume that the stronger interactions between symmetry mates seen in mutant w.e.t. wt protein are the cause of formation of tetrameric population even in the absence of stress in mutant. Further since PISA is predicting it to be  dimer can we predict the structure of higher order oligomerisation state based on symmetry analysis results as well as by doing some mutations at symmetry interface to prove that in solution also, these interactions persists and are responsible for oligomerisation of this protein. Also I want to add that mutations are not in the interaction interface.

 

On Thu, Sep 10, 2015 at 4:51 PM, Pankaj Chauhan <[log in to unmask]> wrote:

Dear Pankaj,

 

PISA is the good suggestion to know the correct symmetry related contacts. 

Is the mutation in between crystal contacts? When you superpose the two structures, do you find any difference in them? There are few questions that can give directions to next experiments to answer any biological question.

 

Pankaj 

 

On Thursday, September 10, 2015, pankaj sharma <[log in to unmask]> wrote:

Dear all,

I am solving crystal structure of a protein. wild type protein is solved in H32 space group but its mutant is in p6522 space group. this protein is known to exist in oligomeric states. Interaction between the symmetry mates of mutant is twice (~86, 10H-bonds, 2 salt bridges) as compared to wild type protein (~46, 4H-bond and 2 salt bridges). Further we carried out native PAGE analysis where we found that an additional band corresponding to oligomeric state is present in mutant protein but absent in wt protein. 

 

So, can we co-relate crystallization data with native PAGE results? or 

we should do further mutations based on crystal structure results? 

 

Further mutant protein exists in two populations native and oligomeric state, thus if the interactions between mutant protein molecules are sufficient to form oligomeric state then why all the mutant protein molecules are not transforming from native to oligomeric state?  

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