Filamentous morphology in GroE-depleted Escherichia coli induced by impaired folding of FtsE

Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, FSB-401, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan

^* To whom correspondence should be addressed. Email: taguchi{at}k.u-tokyo.ac.jp.

	Abstract

The chaperonin GroE (GroEL and the co-chaperonin GroES) is the only chaperone system that is essential for the viability of Escherichia coli. It is known that GroE-depleted cells exhibit a filamentous morphology, suggesting that GroE is required for the folding of proteins involved in cell division. Although previous studies, including proteome-wide analyses of GroE substrates, have suggested several targets of GroE in cell division, there is no direct in vivo evidence to identify which substrates exhibit obligate dependence on GroE for folding. Among the candidate substrates, we found that the prior excess production of FtsE, a protein engaged in cell division, completely suppressed the filamentation of the GroE-depleted E. coli. The GroE depletion led to a drastic decrease of FtsE, and the cells exhibited a known phenotype associated with impaired FtsE function. In the GroE-depleted filamentous cells, the localizations of FtsA and ZipA, which both assemble with the FtsZ septal ring before FtsE, were normal, whereas FtsX, the interaction partmer of FtsE, and FtsQ, which is recruited after FtsE, did not localize to the ring, suggesting that the decrease in FtsE is a cause of the filamentous morphology. Finally, a reconstituted cell-free translation system revealed that the folding of newly translated FtsE was stringently dependent on GroEL/GroES. Taken together, we concluded that FtsE is a target substrate of the GroE system in E. coli cell division.