Fig. 5. Mutational analysis of the binding of DimB to R2. (A) Binding of DimB to an R2 scanning mutant series. The probe is R2 and the unlabelled competitors are scanning mutants of R2. They are labelled M1 to M9 and each contains a four nucleotide substitution, of GCGC, at the indicated position relative to the unmutated R2 sequence. The position of the mutation that produces a major reduction in competition is shown above the R2 sequence. (B) Proposed consensus sequence for DimB binding and comparison with known bZIP binding sites. This is a manually generated alignment of the R1 and R2 binding sites of DimB with that of several bZIP proteins: human AP1 and CREB, fission yeast GCN4 and the two alternate binding sites of budding yeast Pap1 (Fuji et al., 2000). Residues common to at least four out of the seven sequences are in red.