Here is another example of ordering of alpha helix upon metal (nickel) binding.
Nature Structural Biology 10, 794 - 799 (2003) Crystal structure of the nickel-responsive transcription factor NikR Eric R Schreiter, Michael D Sintchak, Yayi Guo, Peter T Chivers, Robert T Sauer & Catherine L Drennan Hector H Hernandez Massachusetts Institute of Technology Chemistry - PhD Candidate 56-546 http://web.mit.edu/hectorh/www/ http://web.mit.edu/cld/ No sensible decision can be made any longer without taking into account not only the world as it is, but the world as it will be. . ... -Isaac Asimov -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Florian Schmitzberger Sent: Tuesday, April 08, 2008 9:03 AM To: [email protected] Subject: [ccp4bb] helix ordering upon metal binding Dear All, Are there prominent examples of ordering of an alpha-helix within a protein upon metal binding (in particular Fe)? In my case, I observe that a 10 amino acid fragment seems to become visible in electron density maps, only upon Fe2+ binding to a glutamate (the first amino acid of the respective 10 residues). The fragment is part of a larger alpha-helix (which is ordered irrespective of metal binding). The 10 residue part (including the Glu) is not visible in the iron-free crystal structure in this subunit of the homodimer. I don't think that the helix is necessarily unfolding/folding, since in the other subunit in the asymmetric unit it is visible in the absence of Fe (probably due to crystal contacts). I am unsure about the significance, as it is only in one of the two subunits in the asym. unit that I see the ordering. Thank you very much in advance for any comments! Florian
