The histone-like HU protein is the major nucleoid-associated protein involved in the dynamics and structure of the bacterial chromosome. Under physiological conditions, the three possible dimeric forms of the E. coli HU protein (EcHU alpha(2), EcHU beta(2), and EcHU alpha beta) are in thermal equilibrium between two dimeric conformations (N-2 a dagger" I-2) varying in their secondary structure content. High-temperature molecular dynamics simulations combined with NMR experiments provide information about structural and dynamics features at the atomic level for the N-2 to I-2 thermal transition of the EcHU beta(2) homodimer. On the basis of these data, a realistic 3D model is proposed for the major I-2 conformation of EcHU beta(2). This model is in agreement with previous experimental data.