Dear Jared, I advise you to have a look into our very recent Nat Comms paper (in particular supplementary information) https://doi.org/10.1038/s41467-020-20596-0
In our high-resolution crystal structures of the light-adapted (6S6C) and dark-adapted (6GUX) state of Archaerhodopsin-3 (AR3), solved to 1.1 Å and 1.3 Å respectively, the N-terminus residue Gln7 is modified to a pyroglutamyl group (PCA). In our paper, we confirm this modification by native mass spectroscopy. The AR3 protein was produce from its natural source and any detergent was used during the purification or crystallisation processes. Crystals were grown at pH5.5. I hope it helps Isabel ------------------------------------------------------------------ Isabel Moraes, PhD Principal Research Scientist - Structural Biology National Physical Laboratory (NPL) Hampton Rd | Teddington | Middlesex | TW11 0LW ------------------------------------------------------------------- ________________________________ From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> on behalf of Jared Sampson <jared.samp...@columbia.edu> Sent: 21 April 2021 16:15 To: CCP4BB@JISCMAIL.AC.UK <CCP4BB@JISCMAIL.AC.UK> Subject: [EXTERNAL] [ccp4bb] N-terminal PCA as artifact of crystallization? CAUTION: This email originated from outside of NPL. Do not click links or open attachments unless you recognize the sender and know the content is safe. Dear all, I'm looking at a crystal structure (1H4G) where the N-terminal Glu residue has cyclized to pyroglutamic acid (PCA). The protein was expressed in and secreted from bacteria (Bacillus licheniformis), and the crystallization conditions for 3 ul hanging drops were 2 ul protein solution (10 mg/ml in 100 mM sodium acetate pH 6.0) + 1 ul reservoir solution (100 mM MES pH 6.5, 30% ammonium sulphate). As I wouldn't typically expect this kind of post-translational modification to appear in bacteria (please correct me if I'm mistaken about this), I suspect the presence of PCA here to be an artifact of crystallization. Have others seen cyclization of N-terminal Glu or Gln to PCA under such acidic crystallization conditions? I'd be interested in seeing any relevant literature you might be able to suggest. Many thanks, Jared ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 Visit the NPL website<https://www.npl.co.uk/?utm_source=Email%20Footer&utm_medium=email&utm_campaign=Homepage> and find out how our cutting-edge measurement science has a positive impact in the real world ________________________________ [http://resource.npl.co.uk/images/npl-logo.jpg]<https://www.npl.co.uk/?utm_source=Email%20Footer&utm_medium=email&utm_campaign=Homepage> Keep in touch<https://www.npl.co.uk/contact> [http://resource.npl.co.uk/images/twitter.jpg] <http://www.twitter.com/npl> [http://resource.npl.co.uk/images/facebook.jpg] <http://www.facebook.com/npldigital> [http://resource.npl.co.uk/images/youtube.jpg] <http://www.youtube.com/npldigital> ________________________________ NPL Privacy Policy<https://www.npl.co.uk/privacy-policy/> If you have received this message in error, please notify us and remove it from your system. NPL Management Ltd cannot guarantee that the e-mail or any attachments are free from viruses. NPL Management Ltd is a company registered in England and Wales, number: 2937881 Registered office: National Physical Laboratory | Hampton Road | Teddington, Middlesex | UK | TW11 0LW ######################################################################## 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/
