Re: Missing tryptophan in N-terminal Sequencing
Daniel Hess (Daniel.Hess@fmi.ch)
Thu, 8 Apr 1999 10:28:52 +0200
>I have a peptide sequence in which the tryptophan is "missing" in the
>cycle where it should have appeared. The original sample was a protein
>digested
>after R&A with endo LYS-C. The peptides were separated on a PE ABI173A
>and the peptide peak sequenced with standard gas-phase Edman Chemistry. I
>do visualize a small peak that co-elutes with PRO. The client assures me
>that this does have a TRP in this position and the rest of the sequence
>matches up 100%.
>
>Any help in this matter?
>
>Thanks,
>Suzanne Perry-Riehm
>
>Suzanne C. Perry, Research Associate
>NAPS Protein Service Laboratory
>Biotechnology Department, University of British Columbia
>CANADA
>phone:(604)822-9662 Fax:(604)822-0676 email:perry@interchange.ubc.ca
>Visit our web page at : www.biotech.ubc.ca/naps/napshome.htm
Can you check the mass of the peptide? If it is correct you probably
destroy the Trp during sequencing. However a modification we often find is
a C-glycosylation with a mannose attached to the c2 of the indole ring of
the Trp. The peptide would have a mass 162 heavier than calculated. The
PTH-TrpMan elutes on the ABI 120 after PTH-Tyr.
With best regards Daniel
Dr. Daniel Hess
Friedrich Miescher Institut
Postfach 2543
CH-4002 Basel
Tel.: 061 697 85 44 or 061 697 68 68 FAX: 061 697 3976
e-mail: dhess@fmi.ch