PMID: 7031062Jan 10, 1982Paper

Role of superhelicity in homologous pairing of DNA molecules promoted by Escherichia coli recA protein.

The Journal of Biological Chemistry
Takehiko ShibataT Ando

Abstract

In the presence of ATP and an excess of recA protein, superhelical closed circular DNA (form I DNA) and homologous single-stranded fragments paired to form D-loops in the early stage of incubation and dissociated during subsequent incubation. RecA protein that was not bound to single-stranded DNA ("free recA protein") was shown to be responsible for the dissociation of D-loops. Larger amount of free recA protein gave a lower final yield of D-loops. When the concentration of form I DNA was increased in the presence of a fixed amount of single-stranded DNA, larger amounts of free recA protein were required to produce a certain extent of dissociation. When form I DNA, excess recA protein, and ATP were incubated without single-stranded DNA, or with heterologous single-stranded fragments before the addition of homologous single-stranded fragments, formation and subsequent dissociation of D-loops were observed as in the case when all components of the reaction were added from the start. Therefore, the dissociation of D-loops is a result of the stoichiometric interaction between free recA protein and form I DNA bearing D-loops. In the process of formation and dissociation of D-loops, form I DNA was converted to an inactive substrate w...Continue Reading

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