Aa. Tokmakov et al., PHOSPHORYLATION-SENSITIVE SECONDARY STRUCTURE IN A SYNTHETIC PEPTIDE CORRESPONDING TO THE ACTIVATION LOOP OF MAP KINASE, Biochemical and biophysical research communications, 236(2), 1997, pp. 243-247
A 26-amino acid long synthetic peptide corresponding to the activation
loop of Xenopus MAP kinase (MAPK), termed IDA (Inter-DFG-APE) MAPK pe
ptide, was found to efficiently inhibit the immunoprecipitation of the
enzyme with anti-IDA MAPK serum. The value of half-inhibition concent
ration (100 nM) indicates that the IDA peptide and native MAPK activat
ion loop are virtually indistinguishable in terms of antibody recognit
ion. On the other hand, the Tyr-phosphorylated form of the peptide exe
rted its inhibitory action at around one order higher concentration Sh
orter nonapeptides covering the epitope sequence of anti-IDA MAPK anti
body could also affect the immunoprecipitation but at much higher conc
entrations (half-inhibition concentration similar to 100 mu M) and ind
ependently of their phosphorylation state. Circular dichroic study rev
ealed that a secondary structure could be readily induced with the aid
of trifluoroethanol in the unphosphorylated and, to a less extent, in
the Tyr-phosphorylated IDA MAPK peptide but not in the shorter nonape
ptides. These results suggest that the secondary structure similar to
that of the unphosphorylated activation loop of MAPK can be formed in
the IDA MAPK peptide and may be lost upon its Tyr-phosphorylation. (C)
1997 Academic Press.