Easy to check whether it is a metal by looking at an anomalous difference map.. But there are examples of di-sulphides formed between symmetry related molecules.. Query the wwwpdb -
On Tue, 21 Jan 2020 at 18:06, Guenter Fritz < guenter.fritz.phenix.c...@gmail.com> wrote: > Dear Chris, are there any metal ions in your buffer or in your protein. We > had a similar looking case. A Zn2+ ion bridged two monomers. Our protein is > a Zn2+ binding protein. The Zn2+ originated from some denatured protein in > the drop. No extra Zn2+ was in the crystallization buffer. > > http://www.rcsb.org/structure/5CHT > https://www.nature.com/articles/nsmb.3371 > HTH > Guenter > > Dear CCP4BB Users, > > I've recently solved the ~2.2 angstrom structure of a protein. In my > electron density there are unusual monomer-monomer interfaces involving > pairs of His and Cys residues (see https://ibb.co/wdWBcdk). Note the > positive Fo-Fc density between the four side chains. As there is not > adequate space for a water molecule or metal ion, perhaps the Cys residues > are partially tied up disulfide bonds? However, the protein looks to be > fully monomeric based on LC-MS measurements. Has anyone else observed > crystal-driven formation of disulfide bridges? > > Aside from this region, there is no extensive interface between momoners, > and PDBePISA suggests a monomeric state. > > Thanks in advance for any advice! > > Best wishes, > Chris > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 > > > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1