To study possible correlations between promoter activity and the structural flexibility of the DNA helix, we have carried Out Unrestrained molecular dynamics simulations of the -10 Consensus region sequence and five variants forming the -10 region of various Escherichia coli promoter sequences. Analyses of the trajectories obtained from the simulations show that the consensus sequence has a pattern Of two structurally flexible nucleotide steps sandwiched between two stiff steps. In the other sequences, this pattern varies ill consonance with the change in the sequence. The variations in the patterns show correlation with the promoter strength. (c) 2006 Elsevier Inc. All rights reserved.