Identification and kinetic analysis of the interaction between Nck-2 and DOCK180

Nck-2 is a newly identified adapter protein comprising three N-terminal SH3 domains and one C-terminal SH2 domain. We have identified in a yeast two-hybrid brid screen DOCK180, a signaling protein implicated in the regulation of membrane ruffling and migration, as a binding protein for Nck-2, Surface plasmon resonance analyses reveal that the second and the third SH3 domains interact with the C-terminal region of DOCK180. The interactions mediated by the individual SH3 domains, however, are much weaker than that of the full length Nck-2. Furthermore, a point mutation that inactivates the second or the third SH3 domain dramatically reduced the interaction of Nck-2 with DOCK180, suggesting that both SH3 domains contribute to the DOCK180 binding. A major Nck-2 binding site, which is recognized primarily by the third St13 domain, has been mapped to residues 1819-1836 of DOCK180. Two additional, albeit much,weaker, Nck-2 SH3 binding sites are located to DOCK180 residues 1793-1810 and 1835-1852 respectively. Consistent with the mutational studies, kinetic analyses by surface plasmon resonance suggest that two binding events with equilibrium dissociation constants of 4.15+/-1.9x10(-7) hi and 3.24+/-1.9 x 10(-9) M mediate the binding of GS5T-Nck-2 to CST fusion protein containing the C-terminal region of DOCK180, These studies identify a novel interaction between Nck-2 and DOCK180, Furthermore, they provide a detailed analysis of a protein complex formation mediated by multiple St13 domains revealing that tandem SH3 domains significantly enhance the weak interactions mediated by each individual SH3 domain. (C) 2001 Federation of European Biochemical Societies. published by Elsevier Science B.V. All rights reserved.