FIG. 2.

Sequence of HgdD is related to those of TolC proteins. (A) Model of HgdD generated as described in the text, showing structural homology to the outer membrane protein TolC. Side, top, and bottom views are shown. Further details are available in the supplemental material. The coordinates are available upon request. (B) Tree of 178 sequences of members of the TolC family (for details, see Fig. S2 in the supplemental material), representing a maximum likelihood phylogeny, assuming the WAG model and constant rates across sites. The tree is based on a multiple alignment. Bar = 0.1 amino acid substitution. The functional categories were assigned as described by Andersen et al. (3). (C) Isolated cell walls (CW) from lysed heterocysts of strain NMP-alr2887-GFP (lane 1) were treated with 8 M urea (lane 2), 0.1 M sodium carbonate (lane 3), or 1 M NaCl (lane 4). The pelleted membrane fraction (P) or the supernatant (S) was probed with antibodies against the outer membrane protein Alr2269 (αalr2269), which was used as a control, or GFP (αGFP). The migration positions of some molecular mass markers (in kDa) are indicated on the right for the pellet fraction probed with anti-GFP.