FIG 2.

ZipA cross-links FtsZ at canonical residues. (A) Anti-ZipA and anti-FtsZ Western blots of WM1074 cell lysates carrying pUltra-pBpF, pKG110-FtsZ, and pDSW210-ZipA-GFP or derived constructs containing indicated Bpa substitutions in ZipA. Canonical site substitutions M226X and F269X produced CLS of moderate intensity compared to the noncanonical site R314X. Cross-linking efficiency relative to ZipA(R314X)-GFP on each blot is indicated below +UV lanes and was normalized by total protein levels and ZipA-GFP expression for each strain. ND, not determined. Each panel shows a composite of two blots. (B) Crystal structure of ZipA (gray) bound to the FtsZ CTP (teal) (16), rotated 180° around a vertical axis compared with the structure in Fig. 1, annotated with each canonical residue tested for cross-linking (purple). Asterisks indicate cross-linking strength relative to the noncanonical site R314X.