Conversation 11: No. 1

category image Volume: Conversation 11
Issue Number 1
May 2000
ISBN 0-940030-80-2

A Mechanism for RecA-Promoted Sequence Homology Recognition and Strand Exchange Between Single-Stranded DNA and Duplex DNA, via Triple-Helical Intermediates

A central function of RecA protein during homologous recombination is to promote sequence recognition and strand exchange between a stretched and unwound single-stranded DNA, to which it is complexed, and a duplex DNA. By studying the properties of DNA under the conditions of deformation imposed by RecA, we propose a model for recognition and strand exchange at the atomic level, via unusual triple-helical intermediates. In this model, association takes place within a stretched and unwound triple helix of a new type, where the invading single strand occupies the minor groove of the duplex in a parallel orientation. Our calculations indicate that strand exchange within this structure is exothermic and results in a triple helix where the third strand interacts in the major groove, the so-called R-DNA triple helix. Preliminary calculations suggest that sequence homology recognition within the triplex of association is partial and that it is completed during strand exchange and product formation.

Guillaume Bertucat
Richard Lavery
and Chantal Prévost

Laboratoire de Biochimie Théorique
Institut de Biologie Physico-Chimique
13, rue Pierre et Marie Curie
75005 Paris, France


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