Several mechanisms are involved in the regulation of cellular signaling. Bruton tyrosine kinase (Btk) of the Tec family contains in the Tec homology (TH) domain a proline-rich region (PRR) capable of interacting with several SH3 domains. The Btk has the SH3 domain adjacent to the TH domain. CD and fluorescence spectroscopy were used to study the binding of two peptides corresponding to segments in the PRR to the Btk SH3 domain. The peptide for the N-terminal half of the PRR binds specifically, whereas the other peptide had hardly any affinity. The TH domain has about four times lower affinity to the SH3 domain than the peptide, 17.0 vs 3.9 microM. The interaction was further tested with an SH3 domain construct that contained the PRR. The two peptides cannot compete for the binding to the extended protein and the TH domain has two times lower affinity to the extended SH3 domain. The intra- or intermolecular interaction between the TH and SH3 domain might have regulatory function also in the other Tec family members.
Copyright 2002 Wiley Periodicals, Inc.