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Boundaries of the nicking region for the F plasmid transfer origin, oriT
Author(s) -
Luo Yanan,
Gao Qian,
Deonier Richard C.
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.tb02353.x
Subject(s) - biology , plasmid , base pair , dna , mutant , genetics , gene , microbiology and biotechnology
Summary The extent of the F plasmid oriT nicking region was determined from the properties of successive substitution mutations in the region from base pair 121 to base pair 174 and from KMnO 4 probing of DNA structural distortions induced in vivo by tra gene products. Nicking and transfer assays indicated that the left margin of oriT Wes predominantly at the nick site, and that the nicking domain primarily lies within 17bp to the right of the nick. Some mutants that were proficient for nicking showed reduced frequencies of termination, indicating that oriT nicking does not guarantee efficient termination. DNA in the vicinity of the nick (G 137 , T 138 , G 140 , and T 141 on the nicked strand) showed elevated sensitivity to KMnO 4 when tra gene products were present in the donor. Bases C 145 , C 146 , C 147 , C 149 , and G 150 on the un‐nicked strand also became more sensitive to oxidation under tra + conditions. The bases preferentially oxidized by KMnO 4 lie within the nicking domain, as defined by the substitution mutants, and they include dinucleotides that can produce kinks in the DNA. Base pairs in the nicking region are calculated to be more thermodynamically stable than base pairs in the flanking regions.