Fox GC, Shafiq M, Briggs DC, Knowles PP, Collister M, Didmon MJ, Makrantoni V, Dickinson RJ, Hanrahan S, Totty N, Stark MJ, Keyse SM, McDonald NQ. Abstract Redox-mediated substrate recognition by Sdp1 defines a new group of tyrosine phosphatases. Nature. 2007 May 24;447(7143):487-92. Epub 2007 May 9. PMID: 17495930
(ahem) We have something similar to what you describe - a disulphide linked N-terminal extension that was invisible, but part of it (including the disulphide bond) was necessary for substrate recognition. We had datasets ± DTT, and were able to confirm the presence of a disulphide my mass spec and free-thiol assays. HTH, David 2008/10/27 Derek Logan <[EMAIL PROTECTED]>: > Hello everyone, > We are working on a protein in which a long loop is held in place by a > disulphide bond. All the biochemistry and biophysics of this protein > indicates that the disulphide bond should be intact, but we only see one end > of it in the crystal structure. The protein has not been exposed to any > reductants. The data were collected at a medium intensity synchrotron source > (MAX-lab in Lund) and the total dose should thus not have been extremely > high. We have even looked at maps calculated from the first half of the > dataset (45 minutes exposure vs. 90) and there is no difference. We have > tried to react the free cysteine with 1mM MeHgCl2 and 10mM iodacetamide, to > no avail. Thus we really think the disulphide is intact even in the > crystal. > Has anyone seen a similar case, where all evidence pointed to an intact > disulphide but it was not visible in the density? > Thanks > Derek > > __________________________________________________________________ > > Derek Logan tel: +46 46 222 1443 > > Associate Professor fax: +46 46 222 4692 > > Molecular Biophysics mob: +46 76 8585 707 > > Centre for Molecular Protein Science > > Lund University, Box 124, 221 00 Lund, Sweden > -- ============================ David C. Briggs PhD Father & Crystallographer http://drdavidcbriggs.googlepages.com/home AIM ID: dbassophile ============================
