An FRT flanked neo cassette was inserted into intron 6 (intron 4 in the paper) and two C to G mutations were inserted into exon 7 (coding exon 6; exon 5 in the paper) via homologous recombination. These mutations replace two central prolines in the proline-rich sequence with alanines (P163A, P166A). Interaction between the mutant protein and the SH3.1 domain of Nck1 is not seen in a pull down assay. Flp mediated recombination removed the neo cassette. (J:192604)