Structure determination using poorly diffracting membrane-protein crystals: the H+-ATPase and Na+,K+-ATPase case
Bjørn P Pedersen1, J Preben Morth, Poul Nissen
1Centre for Membrane Pumps in Cells and Disease, Danish National Research Foundation, Aarhus University, Department of Molecular Biology, Gustav Wieds Vej 10C, DK 8000 Aarhus, Denmark.
Abstract:
An approach is presented for the structure determination of membrane proteins on the basis of poorly diffracting crystals which exploits molecular replacement for heavy-atom site identification at 6-9 A maximum resolution and improvement of the heavy-atom-derived phases by multi-crystal averaging using quasi-isomorphous data sets. The multi-crystal averaging procedure allows real-space density averaging followed by phase combination between non-isomorphous native data sets to exploit crystal-to-crystal nonisomorphism despite the crystals belonging to the same space group. This approach has been used in the structure determination of H(+)-ATPase and Na(+),K(+)-ATPase using Ca(2+)-ATPase models and its successful application to the Mhp1 symporter using LeuT as a search model is demonstrated.
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