| Popis: |
Cell division in Escherichia coli requires the concerted action of at least nine division-specific gene products. The division process can be described as having three distinct phases. The early stage involves the formation of a ring of FtsZ molecules at the mid-point of the cell. This process might involve a second protein, FtsW. During the late stage other division proteins are recruited to the mid-cell and the cytoplasmic membrane, peptidoglycan sacculus and outer membrane invaginate at right angles to the long axis of the cell forming a septum. During the very late stage of cell division the septum is completed and daughter cells separate. One cell division gene, ftsK, has been implicated in this late stage of division. The ftsK44 mutant shows a temperature-sensitive block to cell division and forms filamentous cells at elevated temperatures. The nucleoid distribution within these filaments was unaffected. This work describes the cloning of ftsK and the characterisation of both overexpression and deletion of ftsK. Overproduction of FtsK blocks cell division by either directly or indirectly blocking FtsZ ring formation. Deletion of the N-terminal membrane spanning region of FtsK resulted in a lethal block to cell division. This effect can be reversed by expressing the N-terminal 225 aa of FtsK. Examination of the nucleoids in the filaments that result when FtsK is depleted showed that chromosomal segregation was impaired. The N-terminus of FtsK is dispensible when FtsN, an essential cell division protein, is overproduced. |
