A topological model of Tet(L) highlighting the residues functionally probed in this study. The topology is based on the experimental work of others on Tet(K) (28, 29). The gray bars indicate the positions of Motifs described by Paulsen et al. (17) that are conserved either in both 12-TMS and 14-TMS Drug/H+ families (Motifs A,B,C) or conserved only in 14-TMS (Motifs D1, H, E, F).