CHARACTERIZATION OF INTERACTIONS OF NCK WITH SOS AND DYNAMIN

One of the adaptor proteins, Nck, comprises a single SH2 domain and th ree SH3 domains that are important in protein-protein interactions. Th e in vivo association of Nck with the guanine nucleotide exchange fact or Sos has been well documented; however, the precise nature of the in teraction is unclear. To determine which SH3 domains are involved in t he Nck-Sos interaction, individual SH3 domains of Nck were generated a s glutathione S-transferase fusion proteins. We found that exclusively the third (C-terminal) SH3 domain of Nck has the ability to bind to S os. In addition, in [S-35]methionine labelled K562 cells, a 100,000 M- r protein was found to be associated with the third SH3 domain of Nck. This protein was identified as dynamin, a GTP-binding protein that ha s been implicated in clathrin-coated vesicle formation. Dynamin and Nc k co-precipitated when cell lysates were immunoprecipitated with anti- Nck antibody. These data suggest that Nck may contribute to Ras activa tion and the function of dynamin in membrane trafficking through its t hird SH3 domain. (C) 1998 Elsevier Science Inc.