Ferentz A E, Walker G C, Wagner G
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
EMBO J. 2001 Aug 1;20(15):4287-98. doi: 10.1093/emboj/20.15.4287.
During the SOS response of Escherichia coli to DNA damage, the umuDC operon is induced, producing the trimeric protein complexes UmuD2C, a DNA damage checkpoint effector, and UmuD'2C (DNA polymerase V), which carries out translesion synthesis, the basis of 'SOS mutagenesis'. UmuD'2, the homodimeric 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 crystal structure, even though the topologies of the two structures are quite similar. Most significantly, the active site residues S60 and K97 do not point directly at one another in solution as they do in the crystal, suggesting that self-cleavage of UmuD might require RecA to assemble the active site. Structural differences between UmuD'2 and UmuD'- UmuD suggest that UmuD'2C and UmuD2C might achieve their different biological activities through distinct interactions with RecA and DNA pol III.
在大肠杆菌对DNA损伤的SOS应答过程中，umuDC操纵子被诱导表达，产生三聚体蛋白复合物UmuD2C（一种DNA损伤检查点效应因子）和UmuD'2C（DNA聚合酶V），后者进行跨损伤合成，这是“SOS诱变”的基础。DNA聚合酶V的同二聚体组分UmuD'2由RecA促进的UmuD自切割产生，该切割去除了UmuD的24个N端残基。我们报道了UmuD'2的溶液结构（PDB ID 1I4V）以及在跨损伤合成中无活性的异二聚体UmuD'-UmuD内的相互作用。溶液中UmuD'2的整体形状与先前报道的晶体结构有很大不同，尽管这两种结构的拓扑结构非常相似。最显著的是，活性位点残基S60和K97在溶液中不像在晶体中那样直接相对，这表明UmuD的自切割可能需要RecA来组装活性位点。UmuD'2和UmuD'-UmuD之间的结构差异表明，UmuD'2C和UmuD2C可能通过与RecA和DNA聚合酶III的不同相互作用来实现它们不同的生物学活性。
