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Reinitiation kinetics in eight dnaA (Ts) mutants of Escherichia coli : rifampicin‐resistant Initiation of chromosome replication
Author(s) -
Hansen Flemming G.
Publication year - 1995
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1995.tb02227.x
Subject(s) - dnaa , dnab helicase , mutant , biology , dna replication , protein biosynthesis , mutant protein , origin of replication , microbiology and biotechnology , genetics , dna , rna , gene , helicase
Summary The kinetics of reinitiation of chromosome replication of eight dnaA(Ts) mutants was investigated in an isogenic set of strains. Five mutants ( 167, 46, 601, 606 and 5 ) are classified as reversible, since they can reinitiate at 30 C without protein synthesis, whereas the other three ( 508, 205, 204 ) require protein synthesis. In the presence of protein synthesis, reversible mutants initiate one round of replication rapidly after a shift to 30δC, indicating that they contain active or renaturable DnaA protein. The dnaA508 and dnaA204 mutants also reinitiate chromosome replication rapidly, whereas reinitiation is delayed 15–20min in dnaA205. The dnaA508 and dnaA204 mutants might contain active DnaA protein just below the threshold level at 42δC and only require synthesis of small amounts of new DnaA protein before initiation at 30δC, whereas dnaA205 accumulates DnaA protein for some time at 30δC before reaching the initiation threshold. Three of the reversible mutants ( 5, 601 , and 606 ) exhibited, in addition to the protein synthesis‐independent initiation capacity, an RNA synthesis‐independent initiation capacity. The thermal stability of these initiation capacities is the same as for mutant DnaA protein, strongly suggesting that mutant DnaA protein is responsible for both.