No abstract

A mutation in a newly discovered Escherichia coli cell division gene, ftsK, causes a temperature-sensitive late-stage block in division but does not affect chromosome replication or segregation. This defect is specifically suppressed by deletion of dacA, coding for the peptidoglycan DD-carboxypeptidase, PBP 5. FtsK is a large polypeptide (147 kDa) consisting of an N-terminal domain with several predicted membrane-spanning regions, a proline-glutamine-rich domain, and a C-terminal domain with a nucleotide-binding consensus sequence. FtsK has extensive sequence identity with a family of proteins from a wide variety of prokaryotes and plasmids. The plasmid proteins are required for intercellular DNA transfer, and one of the bacterial proteins (the SpoIIIE protein of Bacillus subtilis) has also been implicated in intracellular chromosomal DNA transfer.Cell division is a much-studied process in Escherichia coli, and a number of division genes and proteins are now well known (17). The cell division-specific proteins include FtsZ, which forms a ring around the inside of the cell membrane during division (9,11,16,39,40,45), and a set of membraneassociated proteins (the products of ftsL, -I, -W, -Q, -A, and possibly others) that include the septum-specific peptidoglycan transpeptidase and transglycosylase, PBP 3 (the ftsI gene product). The action of these proteins results in the formation of a covalently cross-linked double-layered septum across the cell center (43). Splitting of the bonds between the two completed layers (accompanied by invagination of the outer membrane) completes the process of cell division (3,63).A mutant, TOE44, described for the first time in this paper, was originally isolated in a search for conditional mutants that are blocked in cell division but in which the temperaturesensitive period is only a short fraction of the cell cycle (6). The same search produced the first mutations in ftsQ, as well as new ftsI and ftsA alleles (6). This set of mutants has now been rescreened to look for any that have a block at a late stage in division.Many mutations cause an indirect block to cell division because they elicit the SOS response (by interference with DNA replication) and thus induce the synthesis of the FtsZ inhibitor, SfiA (26). Mutations (e.g., in dnaK or groE) that elicit the heat shock response also cause a block in division that can be reversed by increased amounts of FtsZ in some cases (13). Mutants of these kinds appear to be blocked in a very early stage in division, the stage at which FtsZ acts. The remaining mutants in this collection have now been screened for those that are blocked later in division. The present investigation of TOE44 was prompted by the finding that, at 42ЊC, this mutant appears to be blocked at a very late stage. The mutation responsible has been mapped and shown to be in a previously unidentified gene, ftsK, adjacent to lrp, the gene for the leucine-responsive protein (55,(59)(60)(61)(62). We find that the mutant phenotype is specifically suppressed by the deletion o...

When cells of E. coli reach a certain critical length, which is constant in all growth conditions and eqqal to twice the minimum cell length, they abruptly increase their rate of elongation and divide about 20 min later. Chromosome replication terminates at about this same cell length but is not the signal for the change in rate of cell elongation.

SummaryChromosome dimers, formed by homologous recombination between sister chromosomes, normally require cell division to be resolved into monomers by sitespecific recombination at the dif locus of Escherichia coli. We report here that it is not in fact cell division per se that is required for dimer resolution but the action of the cytoplasmic domain of FtsK, which is a bifunctional protein required both for cell division and for chromosome partition.

SummaryThe behaviour of Escherichia coli cells in which all or part of the ftsK gene is under inducible control shows that FtsK protein has two functional domains: an N-terminal part that is required for cell division, and a C-terminal part that is involved in chromosome localization within the cell.