FIG. 7.

IS21 members. Shown is the phylogeny of the IS21 family and comparison of a representative set of terminal IRs. The top panel shows the organization of a typical IS21 family member. Red boxes, terminal IRs; yellow boxes, ORFs (IstA is the Tpase, and IstB is a regulatory protein). The overlap between these ORFs is indicated as a possible control region where translational coupling might be required for expression of istB. The terminal repeated sequences L1, L2, R1, and R2 are indicated by small arrows. The Archaea have been color coded as follows for clarity: methanogens, blue. Bacteria are indicated in black.