TI  - Specific binding of the transglutaminase, <prot>platelet factor XIII</prot>, to <prot>HSP27</prot>.
PG  - 22379-84
AB  - <prot>HSP27</prot>, the unique mammalian low molecular weight heat shock protein, is
      prominently phosphorylated upon activation of a wide variety of cells and
      has a role in thermotolerance, growth events, and regulation of actin
      cytoskeletal dynamics. In thrombin-stimulated platelets, <prot>HSP27</prot> is rapidly
      and prominently phosphorylated in a manner highly correlated with platelet
      secretion. However, the function of <prot>HSP27</prot> and the identity of proteins
      that interact with <prot>HSP27</prot> remain unknown. To identify specific
      <prot>HSP27</prot>-protein interactions, a recombinant fusion protein affinity reagent
      was constructed and used to identify proteins associating with <prot>HSP27</prot> from
      human platelet lysates and erythroleukemia cells. An 84-kDa protein was
      found to associate specifically with <prot>HSP27</prot> and was isolated from platelet
      lysates, resolved on preparative gels, transferred to nitrocellulose,
      subjected to enzymatic digestion, and microsequenced. A 20-amino acid
      sequence derived from p84 proved identical to amino acids 484-503 of the
      transglutaminase, platelet Factor XIII. Immunoblotting studies were used
      to confirm the binding of  <prot>FXIII</prot>  from fresh platelet lysates to the  <prot>HSP27</prot> 
      fusion protein.  <prot>FXIII</prot>  also was shown to coprecipitate with  <prot>HSP27</prot>  in
      immunoprecipitation studies and to colocalize with <prot>HSP27</prot> in
      immunofluorescence studies of intact glass-activated platelets. The data
      thus demonstrate specific binding of platelet  <prot>FXIII</prot>  to  <prot>HSP27</prot>  and suggest
      that  <prot>HSP27</prot>  may participate in the cellular localization and/or enzymatic
      regulation of platelet  <prot>FXIII</prot> .
AD  - Molecular Cardiology Research Center, New England Medical Center, Tufts,
