Function, Structure, and Evolution of the Major Facilitator Superfamily: The LacY Manifesto
Figure 9
The evolutionary mix-and-match approach for the MFS. (a) Structure overview of FucP (PDBid 3O7Q) and LacY (PDBid 2V8N). Helices are color-coded according to the symmetry motifs: helices I–III: blue; helices IV–VI: green; helices VII–IX: orange; and helices X–XII: yellow. White and gray flags indicate cytoplasmic and periplasmic loops within the symmetry motifs, respectively. The positions of Asp46 (violet sphere in FucP) and Glu325 (red sphere in LacY) are indicated. (b) Schematic representation of the helix triplets in consecutive order in the sequence. Boxes represent the helices and are colored the same as in (a). The flags indicate the loops within symmetry motifs according to A and B. The positions of Asp46 and Glu325 are indicated by violet and red arrows, respectively. (c) Alternative aliments of FucP structure symmetry motifs on LacY structure symmetry motifs. Respective rmsds of the atoms are indicated in blue for each superposition. The sequence similarity/identity for the combination of segment superimpositions for the 92 transport activity relevant positions (side-chain similarity matrix: AVLI, FYW, CM, ST, KRH, DENQ, and PG) is shown at the bottom. The best sequence alignment (superimposition 4) is highlighted in red.
