Re: PROTSEQ: unknown amino acid
Gregory Grant (ggrant@pharmdec.wustl.edu)
Tue, 16 Feb 1999 14:39:39 -0600
>Dear All,
>
>I was sequencing a strange plant protein the other day when my nice
>easy-to-read sequence suddenly produced an unrecognizeable amino acid for 6
>cycles before returning to standard amino acids. Some 8 residues later
>another
>string of 5 more of this unknown appeared. It elutes as three peaks on a
>Procise with buffer A3/B2/premix. The biggest elutes after ALA and the other
>two, which are half its size, elute between GLU and HIS. Can anyone offer
>some
>possible clues as to the identification of this.
>
>Many thanks in advance
>
>Mike
>
>
>-------------------------------------------------------------
>
>Dr Mike Naldrett
>Protein Sequencing & Peptide Synthesis Facility
>John Innes Centre(NFL)
>Norwich Research Park
>Colney
>Norwich
>NR4 7UH
>
>tel 01603-456900 x 2773/2724
>fax 01603-454970
>
>e-mail: mike.naldrett@bbsrc.ac.uk
Mike,
My guess is you are dealing with hydroxyproline which is quite
common in plant proteins. However, hydroxyproline usually only gives the
two peaks flanking Ala. This comes about because of the alternate
stereochemistry of the OH group. I suppose the third peak could come from a
positional isomer of the OH, i.e. 3 and 4 hydroxyproline but I don't know
that for sure. Best bet is to by some of each and run them on your
sequencer. If you do, let us know the result for the ABRF's PTH-aa book
Greg
Gregory A. Grant
ggrant@pharmdec.wustl.edu