FIGURE 6.

Model for the membrane topology of Hhat. A, graphical representation of the topology of human Hhat generated with Protter Server (31). The boundaries of TMDs were designated using output from MemBrain (20). The boundaries of the first re-entrant loop (residues 95–119) are determined as discussed in the Discussion. The area of high conservation (residues 196–234) among MBOAT enzymes with protein substrates is highlighted in yellow. The invariant His-379 residue is shown in red, and the highly conserved Asp-339 is shown in green. Positions of FLAG epitope and HA epitope insertions (asterisks) are indicated along with the corresponding residue numbers. B, graphic representation of the topology of human Hhat (left) and human GOAT as previously described (19) (right) generated with Protter Server. The conserved His and Asp residues are shown in red and yellow, respectively. The topological organization of the C-terminal regions of Hhat and GOAT are highly conserved (below the dotted line).