You might be interested in some work done on NikA, which binds a nickel complex with a small organic ligand. They tentatively identified the ligand as butane-1,2,4-tricarboxylate.
http://www.rcsb.org/pdb/explore.do?structureId=3e3k Good luck, Arthur On Aug 8, 2012, at 4:56 AM, Mario Sniady wrote: > While building our crystal structure model we encountered density which we > weren't able to assign. The unknown molecule/molecules seems to coordinate a > Ni2+-ion. This ion is also coordinated by a histidin and probably one > H2O-molecule. The crystals have been grown from a protein-complex including > the carotinoid peridinin, the lipid DGDG and Chlorophyll. Besides this the > solution in which they have been grown contains Tris pH 8.5, NiCl2 and PEG > 2000 MME. > The linked images show a rotation around the density in 90°-steps (1.1A, > 1.2sigma contour level). The above mentioned H2O-molecule has been removed. > It is supposed to fill the density that is below the Ni2+-Ion in the first > picture. > Images: http://www.bioxtal.rub.de/myst.html.en > Any hints are welcome =) > > Mario
