Compensation for the loss of the conserved membrane targeting sequence of FtsA provides new insights into its function.
The bacterial actin homologue FtsA has a conserved C-terminal membrane targeting sequence (MTS). Deletion or point mutations in the MTS, such as W408E, were shown previously to inactivate FtsA function and inhibit cell division. Because FtsA binds to the tubulin-like FtsZ protein that forms the Z ring, it is thought that the MTS of FtsA is required, along with the transmembrane protein ZipA, to assemble the Z ring and anchor it to the cytoplasmic membrane. Here, we show that despite its reduced membrane binding, FtsA-W408E could localize to the Z ring and recruit the late cell division protein FtsI, but was defective in self-interaction and recruitment of FtsN, another late cell division protein. These defects could be suppressed by a mutation that stimulates membrane association of FtsA-W408E, or by expressing a tandem FtsA-W408E. Remarkably, the FtsA MTS could be completely replaced with the transmembrane domain of MalF and remain functional for cell division. We propose that FtsA function in cell division depends on additive effects of membrane binding and self-interaction, and that the specific requirement of an amphipathic helix for tethering FtsA to the membrane can be bypassed.
Shiomi
Daisuke
D
Microbiology and Molecular Genetics, University of Texas Medical School, 6431 Fannin, Houston, TX 77030, USA.
Margolin
William
W
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D019943:Amino Acid Substitution; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D046915:Penicillin-Binding Proteins / Q000378:metabolism; D046928:Peptidoglycan Glycosyltransferase / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic; D017384:Sequence Deletion; D020798:Two-Hybrid System Techniques
D018528:ATP-Binding Cassette Transporters; D029968:Escherichia coli Proteins; C489310:FtsA protein, E coli; C478704:FtsI protein, E coli; C098711:FtsN protein, E coli; C076835:FtsZ84 protein, E coli; C461639:MalF protein, E coli; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D046915:Penicillin-Binding Proteins; D046928:Peptidoglycan Glycosyltransferase