toy_test.txt

Detection of protein-protein interactions has previously been a balance between specificity ( background reduction ) and affinity ( detection of weak interactions ) .
Recently , the introduction of stable isotope labeling ,
to distinguish specific from unspecific interaction partners ( Blagoev et al , 2003 ; Ranish et al , 2003 )
Based on this principle , we have developed a proteomic screen for peptide motif-based interactions ( Schulze and Mann , 2004 ) .
Using synthetic peptide pairs in phosphorylated and unphosphorylated form
, pull-down experiments are performed to enrich specific binding partners to the phosphorylated bait peptides .
These proteins are subsequently identified and quantified by mass spectrometry .
In this study , by further method development , we greatly increased the throughput of the analysis allowing
us to profile the entire phosphotyrosine interactome of the ErbB-receptor family

Two recent reports suggested a correlation between p130CAS phosphorylation level and cell migration rate .
In both studies , a kinase was transfected in the cells .
One used v-Src , for which p130CAS is a direct substrate ( Fincham and Frame , 1998 ) ,
while the other overexpressed FAK , that , once activated , binds both c-Src and its substrate p130CAS ( Cary et al. , 1998 )
In both studies , hyperphosphorylation of p130CAS was associated with an increase in rate of migration .
Since p130CAS is a substrate for PTP-PEST ( Garton et al. , 1996 )
, removal of this PTP results in hyperphosphorylation of p130CAS ( Cote et al. , 1998 ) .
We decided
to investigate whether the absence of this PTP would result in a change in the motility of these cells
The two cell lines used were heterozygous and homozygous for the PTP-PEST deletion .
To minimize any dominant negative effects from the targeted allele
, comparisons were made between the homozygous and the heterozygous cell lines .