Suppressor genes of a dnaA temperature sensitive mutation in Escherichia coli

Recombinant plasmids were constructed from EcoRI digests of Escherichia coli chromosomal DNA and pMB9 DNA by selecting for suppression of a dnaA-T46 temperature-sensitive mutation. Two types of plasmid capable of suppressing the dnaA mutation were isolated. They did not carry any genetic markers around dnaA and physical mapping with various restriction enzymes showed that neither of the plasmids contained the dnaA gene. One plasmid, pYT47, was characterized further and the protein responsible for the suppression was identified by two-dimensional gel electrophoresis. The molecular weight of the suppressor protein was about 68 Kdal and thus is clearly different from the dnaA gene product.