Ae. Ferentz et al., Converting a DNA damage checkpoint effector (UmuD(2)C) into a lesion bypass polymerase (UmuD ' C-2), EMBO J, 20(15), 2001, pp. 4287-4298
During the SOS response of Escherichia coli to DNA damage, the umuDC operon
is induced, producing the trimeric protein complexes UmuD(2)C, a DNA damag
e checkpoint effector, and UmuD'C-2 (DNA polymerase V), which carries out t
ranslesion synthesis, the basis of 'SOS mutagenesis'. UmuD'(2), the homodim
eric component of DNA pol V, is produced from UmuD by RecA-facilitated self
-cleavage, which removes the 24 N-terminal residues of UmuD. We report the
solution structure of UmuD'(2) (PDB ID 1I4V) and interactions within UmuD'-
UmuD, a heterodimer inactive in translesion synthesis. The overall shape of
UmuD'(2) in solution differs substantially from the previously reported cr
ystal structure, even though the topologies of the two structures are quite
similar. Most significantly, the active site residues S60 and K97 do not p
oint directly at one another in solution as they do in the crystal, suggest
ing that self-cleavage of UmuD might require RecA to assemble the active si
te. Structural differences between UmuD'(2) and UmuD'-UmuD suggest that Umu
D(2)C and UmuD(2)C might achieve their different biological activities thro
ugh distinct interactions with RecA and DNA pol III.