Interaction of Cf-9 C-terminal peptide with CITRX. The C-terminal cytoplasmic domain of Cf-9 was tested for interaction with the full-length CITRX clone (CITRXfl) and several deletion mutants (CITRX150, CITRX120, CITRX90, CITRX60 and CITRX30, amino acids M1-D150, M1-L120, M1-I90, M1-G60, M1-Y30, respectively). Interaction between the Cf-2 C-terminal domain and CITRX was also tested. Interactions between proteins were assayed after 2 days by growth on synthetic dropout plates lacking leucine (activation of the LEU2 reporter gene; Leu−) and β-galactosidase activity, detected as blue colour in plates containing X-gal (activation of the lacZ reporter gene; X-gal+).