>peptide-bond between LYS/ARG and PRO. Now, I also tell my students
that
>this bond is not cleaved at all. However, in a recent LC/MS analysis
we
>measured the masses of two peptides that indicated a tryptictic
cleavage
>exactly at this bond (Enzyme: mod. trypsin from Promega). Since I
could not
>believe it we additionally sequenced the peptides by Edman degradation
and
>it turned out that trypsin has cleaved the LYS-PRO bond.
>On the C-terminal side of the cleavage site there were a number of
GLY
>residues. Does anybody know if this may influences the specificity of
the
>enzyme? Were my supervisors wrong and trypsin does cleave LYS/ARG-PRO
bonds?
>
>best regards
>Petre
>
Peter,
We have seen the same phenomenon when beta-actin is digested with
trypsin (same batch as you)! With MALDI-MS,we always measure a
peptidemass of 945 da and after PSD-analysis it turns out that this
peptide has the sequence AVFPSIVGR which in the actin sequence is
followed by a proline residue and by RHQGVMVGMGQK.
I don't know whether certain amino acids may influence tryptic cleavage
at R/K-P bonds, but I have seen the same phenomenon like you did.
Kris
Kris Gevaert
Flanders Interuniversity Institute for Biotechnology (V.I.B.)
Department of Medical Protein Chemistry
K.L. Ledeganckstraat 35
B-9000 Ghent
Belgium
Europe
Tel.: +32 - 9 264 52 91
Fax: +32 - 9 264 52 79