NMR assignments and secondary structure of the UvrC binding domain of UvrB

The 55 residue C-terminal domain of UvrB that interacts with UvrC during ex cision repair in Escherichia coli has been expressed and purified as a (His )(6) fusion construct. The fragment forms a stable folded domain in solutio n. Heteronuclear NMR experiments were used to obtain extensive N-15, C-13 a nd H-1 NMR assignments. NOESY and chemical shift data showed that the prote in comprises two helices from residues 630 to 648 and from 652 to 670. N-15 relaxation data also show that the first 11 and last three residues are un structured. The effective rotational correlation time within the structured region is not consistent with a monomer. This oligomerisation may be relev ant to the mode of dimerisation of UvrB with the homologous domain of UvrC. (C) 1999 Federation of European Biochemical Societies.