Evidence for Elongation of the Helical Pitch of the RecA Filament Upon ATP and ADP Binding Using Small-Angle Neutron Scattering
Journal article, 1995

Structural changes of the RecA filament upon binding of cofactors have been investigated by small-angle neutron scattering. Both ATP and ADP increased the helical pitch of the RecA homopolymer, which is observed to be 7 nm in the absence of any cofactor. The binding of ATP altered the pitch to 9 nm, whereas the binding of ADP only produced a pitch of 8.2 nm. The pitch determined for the RecA complex with the ATP analog adenosine 5'-[gamma-thio]triphosphate was similar to that found with ATP. Thus, at least three, somewhat different, RecA helical filamentous structures may form in solution. The binding of DNA to RecA did not alter the pitch significantly, indicating that the cofactor binding is the determining factor for the size of the helical pitch of the RecA filament. We also found that elongation of the helical pitch is a necessary, but not a sufficient condition, for the coprotease activity of RecA. The presence of acetate or glutamate ions is also required. The pitch of the ADP . RecA filament is in agreement with that found in the crystal structure. This correlation indicates that this structure corresponds to that of the ADP . RecA filament in solution, although this is not the species active in recombination.


double-stranded dna




small-angle neutron scattering

lexa repressor

cofactor binding

reca filament

lambda repressor


linear dichroism






C. Ellouze

M. Takahashi

Pernilla Wittung

Department of Physical Chemistry

K. Mortensen

M. Schnarr

Bengt Nordén

Department of Physical Chemistry

European Journal of Biochemistry

0014-2956 (ISSN)

Vol. 233 2 579-583

Subject Categories

Biochemistry and Molecular Biology



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