Fig. 3.

The predicted regulation of ribosomal proteins by zinc. (Upper) Zn-rich conditions. The ribosomes contain the protein with functional Zn ribbon (black circles), and transcription of the gene encoding the paralog (gray arrow) is inhibited by the zinc repressor (ZUR or AcdR, black rectangle) bound to the upstream recognition site (double arrow). (Lower) Zn-depleted conditions. The paralog gene is expressed (broken arrow), and the protein is incorporated into a fraction of ribosomes (gray circles), thus releasing zinc (dotted arrow) for incorporation into Zn-dependent enzymes (triangles).