Exact methods for lattice protein models

Lattice protein models are well studied abstractions of globular proteins. By discretizing the structure space and simplifying the energy model over regular proteins, they enable detailed studies of protein structure formation and evolution. But even in the simplest lattice protein models, the prediction of optimal structures is computationally hard. Therefore, often heuristic approaches are applied to find such conformations. Commonly, heuristic methods find only locally optimal solutions. Nevertheless, there exist methods that guarantee to predict globally optimal structures. Currently only one such exact approach is publicly available, namely the Constraint-based Protein Structure Prediction (CPSP) method and variants. Here, we review exact approaches and derived methods. We discuss fundamental concepts like hydrophobic core construction and their use in optimal structure prediction as well as possible applications like combinations of different energy models.