Where would it get the sulphate to make sulphonate? Was there sulphate somewhere in the purification?
Maybe it's a phosphate gotten off the FMN? I guess the phospho-cys bond might be a bit longer? JPK Analyst.<https://www.ncbi.nlm.nih.gov/pubmed/25011562> 2014 Sep 7;139(17):4118-23. doi: 10.1039/c4an00724g. Puzzling over protein cysteine phosphorylation--assessment of proteomic tools for S-phosphorylation profiling. Buchowiecka AK<https://www.ncbi.nlm.nih.gov/pubmed/?term=Buchowiecka%20AK%5BAuthor%5D&cauthor=true&cauthor_uid=25011562>1. Author information<https://www.ncbi.nlm.nih.gov/pubmed/25011562> Abstract Cysteine phosphorylation has recently been discovered in both prokaryotic and eukaryotic systems, and is thought to play crucial roles in signaling and regulation of cellular responses. This article explores the topics of chemical stability of this type of structural modification and the resulting issues regarding affinity enrichment of S-phosphopeptides and their mass spectrometry-based detection in the course of general proteomics studies. Together, this work suggests that the current advances in phosphoproteomic methodologies provide adequate tools for investigating protein cysteine phosphorylation and appear to be immediately available for practical implementation. The article provides useful information necessary for designing experiments in the emerging cysteine phosphoproteomics. The examples of methodological proposals for S-linked phosphorylation detection are included herein in order to stimulate development of new approaches by the phosphoproteomic community. From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Antonio Ariza Sent: Wednesday, May 17, 2017 4:04 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] CYS modification and choice of PEG I haven't asked anything for a loooooong time, so here are a couple of question "for the honourable members of the esteemed CCP4 bulletin board" ... or as I'd usually say: "for y'all". ;) 1) I have this modified CYS in one of the structures I'm working on and ... I'm quite unhappy with it (see attached pics). At first I thought it was cacodylate ... but alas, no cacodylate was used during purification or crystallisation. So I looked up possible modifications on CYS residues and I came up with cysteine-s-sulfonic acid (CSU). This looks good in principle but it doesn't quite fit the electron density as the bond between the two sulphur atoms is too short. The average length for an S-S bond is about 2.05 Ang and refmac refines this one to 1.97 Ang, but it looks like it should be at least 2.5 Ang to sit correctly in the electron density. Also, there is some negative density in there, suggesting that maybe it's something with fewer electrons than a sulfonic acid ... or maybe it has less than 100% occupancy. Any suggestions? The condition contains TRIS, bicine, NaCl, NaFl, NaI, DTT, FMN, PEG 500 MME and PEG 20,000. 2) There are two partial PEG molecules in this structure. I've initially modeled two PEG 400 (PE4) molecules into the density (simply because I remembered the 3 -letter code for it) and removed the excess atoms from them. However, since there is a mixture of PEG 500 MME and PEG 20,000 in the condition, what would you recommend I use instead of PE4? Cheers, Tony ------------------------------------------------------ Dr. Antonio Ariza University of Oxford Sir William Dunn School of Pathology South Parks Road Oxford OX1 3RE e-mail: antonio.ar...@path.ox.ac.uk<mailto:antonio.ar...@path.ox.ac.uk> Tel: 00 +44 1865 285655 Links to my public profiles: ResearchGate<https://www.researchgate.net/profile/Antonio_Ariza> LinkedIn<https://www.linkedin.com/in/antonioariza1> GoogleScholar<https://scholar.google.co.uk/citations?user=9pAIKV0AAAAJ&hl=en> Twitter<https://twitter.com/DrAntonioAriza?lang=en> Check out my latest paper!!! The toxin-antitoxin system DarTG catalyzes reversible ADP-ribosylation of DNA<http://www.cell.com/molecular-cell/abstract/S1097-2765(16)30722-5>
