Termination of DNA replication in Bacillus subtilis involves the polar arrest of replication forks by a specific complex formed between the dimeric 29 kDa replication terminator protein (RTP) and DNA terminator sites. We have used NMR spectroscopy to probe the changes in H-1- N-15 correlation spectra of a N-15-labelled RTP.C100S mutant upon the addition of a 21 base pair symmetrical DNA binding site. Assignment of the H-1- N-15 correlations was achieved using a suite of triple resonance NMR experiments with N-15,C-13,70% H-2 enriched protein recorded at 800 MHz and using TROSY pulse sequences. Perturbations to H-1-N-15 spectra revealed that the N-termini, alpha 3-helices and several loops are affected by the binding interaction. An analysis of this data in light of the crystallographically determined apo- and DNA-bound forms of RTP.C100S revealed that the NMR spectral perturbations correlate more closely to protein structural changes upon complex formation rather than to interactions at the protein-DNA interface. (c) 2005 Elsevier Inc. All rights reserved.