Efficient transcription of ribosomal protein (RP) and glycolytic genes requires the Rap1p/Gcr1p regulatory complex. A third factor, Gcr2p, is required for only the glycolytic (specialized) mode of transcriptional activation. It is recruited to the complex by Gcr1p and likely mediates a change in the phosphorylation state and/or conformation of the latter. We show here that leucine zipper motifs...