A simple approach is proposed to investigate the protein structure. Using a low complexity model, a simple pairwise interaction and the concept of global optimization, we are able to calculate ground states of proteins, which are in agreement with experimental data. All possible model structures of small proteins are available below a certain energy threshold. The exact low-energy landscapes for the trp cage protein (1L2Y) is presented showing the connectivity of all states and energy barriers. (c) 2006 Elsevier B.V. All rights reserved.