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 Å 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 Ca2+-ATPase models and its successful application to the Mhp1 symporter using LeuT as a search model is demonstrated.
|Acta Crystallographica Section D: Biological Crystallography
|Udgivet - 12 feb. 2010