GDP
An open reading frame (ORF) encoding a
putative GDP-mannose pyrophosphorylase (SsoGMPP) was identified on the genome sequence of Sulfolobus solfataricus P2, the
predicted gene product showing high amino acid sequence homology to several archaeal, bacterial, and eukaryal
GDP-mannose pyrophosphorylases such as guanidine diphosphomannose pyrophosphorylases
(GMPPs) from Saccharomyces cerevisiae and Arabidopsis thaliana. The sequence was PCR
amplified from genomic DNA of S. solfataricus P2 and heterologous gene expression obtained as a fusion to
glutathione S-transferase in Escherichia coli, under
conditions suitable to reduce the formation of inclusion bodies. Specific
assays performed at 60 degrees C revealed the presence of the archaeal synthesizing GDP-mannose enzyme activity in the
cell extracts of the transformed E. coli. As a positive control, the same
assays were performed at the mesophilic enzyme
optimum temperature on the already characterized yeast recombinant GMPP. The
recombinant protein was purified to homogeneity by glutathione sepharose affinity chromatography and its thermophilic nature could be verified. The enzyme was
definitively identified by demonstrating its capability to catalyze also the
reverse reaction of pyrophosphorolysis and, most
interestingly, its high specificity for synthesizing GDP-mannose.
PMID: 15145064 [PubMed - in process]
Cyclic phosphopeptides were prepared using ring-closing metathesis followed by phosphorylation. These cyclic phosphopeptides were designed to interact with the SH2 domain of Grb2, which is a signal transduction protein of importance as a target for antiproliferative drug development. Binding of these peptides to the Grb2 SH2 domain was evaluated by a surface plasmon resonance assay. High affinity binding to the Grb2 SH2 domain was maintained upon macrocyclization, thus indicating that this method can be used to assemble high affinity cyclic phosphopeptides that interfere with signal transduction cascades.