ENHANCED AFFINITIES AND SPECIFICITIES OF CONSOLIDATED LIGANDS FOR THESRC HOMOLOGY (SH)3 AND SH2 DOMAINS OF ABELSON PROTEIN-TYROSINE KINASE

The possible interrelationships between multiple domains of proteins i nvolved in intracellular signal transduction are complex and not easil y investigated. We have synthesized a series of bivalent consolidated ligands, which interact simultaneously with the SH2 and SH3 domain of Abelson kinase in a SH(32) dual domain construct, a portion of native Abelson kinase. Affinities were measured by quenching of intrinsic try ptophan fluorescence, Consolidated ligands have enhanced affinity and specificity compared to monovalent equivalents. Affinity is also depen dent on the length of the linker joining the two parts, with an optimu m distance similar to that expected from structural models of Abl (SH( 32). These results suggest that consolidated ligands may be generally useful reagents for probing structural and functional activities of mu ltidomain proteins.