This density does not look at all like O-glycosylation. Best regards, Herman
________________________________ From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Savvas Savvides Sent: Wednesday, November 24, 2010 2:48 PM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Strange density on Serine oxygen. Hi Vinson is O-glycosylation possible at all given the origin of the protein and the expression system used? best Savvas On 24 Nov 2010, at 14:42, Vinson LIANG wrote: Dear Savas and all, Thank you very much for all your quick suggestions. I have tried Tyr and it turns out to fit the density very well. I will have the protein sequenced again to see if it is wrong sequece or O-linked glycosylation. I'll let you know if it turns out to be O-linked glycosylation. All the best, Vinson ________________________________ 发件人: Savvas Savvides <savvas.savvi...@ugent.be> 收件人: Vinson LIANG <lwg_conrad_1...@yahoo.com.cn> 抄 送: CCP4BB@JISCMAIL.AC.UK 发送日期: 2010/11/24 (周三) 9:27:31 下午 主 题: Re: [ccp4bb] Strange density on Serine oxygen. Hi Vinson Beyond the possibility for another type of residue as already suggested by Phil and Mark, there is also the possibility of O-linked glycosylation of the serine and threonine, if your protein undergoes such post-translational modification and it has been expressed via an expression system that processes the protein in that way. Ser/Thr tandems are well known targets for O-glycosylation (http://www.cbs.dtu.dk/databases/OGLYCBASE/). best regards Savvas ---- Savvas Savvides Unit for Structural Biology @ L-ProBE Ghent University K.L. Ledeganckstraat 35, 9000 Ghent, Belgium Ph. +32 (0)472 928 519 http://www.LProBE.ugent.be/xray.html On 24 Nov 2010, at 13:10, Vinson LIANG wrote: Dear all, I'm refining a structure and find some strange triangle density on the oxygen of Ser and Thr at the C terminus. One picture of the strange density is attached here. Could anyone please give me some suggestions on what this could be? The buffer used during purification is PBS, Tris and NaCl. And crystallization condition contains PEG3,350 and Mg(NO3)2. Thank you all in advance for any suggestion. Best, Vinson Liang <triangle_density.gif>