Do you mean the sulfur atom density is larger, or do you mean there is a density peak adjacent to the sulfur atom? It is possible for cysteine (CYS) residues to be oxidized to S-hydroxycysteine (CSO) under certain storage or crystallization conditions. Ran into this in a cysteine hydrolase structure.
Roger Rowlett Gordon & Dorothy Kljne Professor, Emeritus Department of Chemistry Colgate University On Wed, Aug 10, 2022, 11:00 AM Thomas, Leonard M. <lmtho...@ou.edu> wrote: > Hello All, > > I have run into something odd. In working on a structure for one of the > groups I work with regularly, on one of the cystine residues I have a very > large positive density peak at the sulfur position. The B value is > approximately 4 times the other values in the residue and on other cystine > residues. The overall structure has 2 molecules in the asymmetric unit > and the corresponding cystine on the other monomer is behaving as I would > expect. There are no disulfides in the structure. > > The data were collected on 9-2 at SSRL and all three of the data sets we > collected show the same thing, all data go to about 2.2 angstroms. We are > trying to determine the ligand binding in the molecule but this cystine is > not involved in ligand binding. In house and other synchrotron data from > previous protein preps and data collection runs of the same molecule grown > in very similar condition and crystallized in the same space group have the > residue behaving normally. > > I am open to any ideas as to what may be going on as I am rather puzzled > by this. > > Thanks for any input, > Len Thomas > > Leonard Thomas, Ph.D. > Biomolecular Structure Core, Director > Oklahoma COBRE in Structural Biology > Price Family Foundation Institute of Structural Biology > University of Oklahoma > Department of Chemistry and Biochemistry > 101 Stephenson Parkway > Norman, OK 73019-5251 > Office: (405)325-1126 > lmtho...@ou.edu > http://www.ou.edu/structuralbiology/cobre-core-facilities/mcl > > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
