Dear All, As usual the bulletin board has been enormously helpful. To remind you here was my original post:
We have solved a structure that has an intersubunit His-His H-bond (ND1---NE2). The protein most likely undergoes conformational changes that involve the making and breaking of H-bonds at this interface. In all the protein structures I have previously studied I don't recall ever seeing such a bond - His-His ring stacking yes, but never H-bonding. I was wondering if anyone else had seen this type of interaction and whether it had any functional significance. The crystals were grown at pH 5.6. --------- It appears that such interactions, although probably not common, tend to occur at interfaces or other structurally/functionally important sites. Here are all the responses I received: ------------------------- >From Esko Oksanen: Dear Dave, Is this what you mean? This occurs in the dimer interface of yeast inorganic pyrophosphatase, I think also in other crystal forms (e.g. 1E9G). This is 2IHP, His 87. Esko (there was an image attached showing an ND1---ND1 type interaction) --------------------------- >From Dirk Kostrewa: Dear David, have a look at the Ammonium Transporter structure, AmtB, PDB entries 1XQE, 1XQF by Zheng et al. or 2NMR and so on by Javelle et al. (search for AmtB on www.pdb.org). We've seen such an unusual shared hydrogen bond between two histidines in the middle of the ammonia channel. Best regards, Dirk. ---------------------------- >From Wim Burmeister: Dear David, why not, as long as the histidine residues are not fully protonated, and at pH 5.6 this is still possible, the nitrogen atoms act as hydrogen bond donors or acceptors. Look for example in pdb 1FL1 KSHV protease, where there is a catalytic triad Ser114-His46-His134. Yours Wim Burmeister ---------------------------- >From Stephen Graham: Dear Dave, I have seen such inter-subunit His-His H-bonds before. See paragraph 2 of section 3.3 of the attached paper for a bit of a discussion... Cheers, Stephen (there was a PDF attached which I can forward to anyone who is interested) ---------------------------- >From V.S. Gowri: Hi, Please see the following reference. Does this answer your query? http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1999/121/i22/abs/ja99034 0o.html regards, gowri. --------------------------- >From Ian Ollmann: Histidine H-bond networks are sometimes used for facile proton migration between distal acid base pairs, especially in catalysis. You might look to see what is on the other side of each histidine. Ian --------------------------- Thanks once again BB!! Dave Lawson ------------------------------- Dr. David M. Lawson Biological Chemistry Dept., John Innes Centre, Norwich, NR4 7UH, UK. Tel: +44-(0)1603-450725 Fax: +44-(0)1603-450018 Email: [EMAIL PROTECTED] Web: http://www.jic.bbsrc.ac.uk/staff/david-lawson/index.htm
